Soal coding javascript untuk latihan

Klik⭐jika Anda menyukai proyek ini dan ikuti @SudheerJonna untuk pembaruan lainnya. Pertanyaan pengkodean tersedia. Versi PDF dan Epub tersedia di tab tindakan

Jelajahi sumber daya gratis terbaik untuk mempelajari JavaScript. Bangun proyek Anda sendiri & dapatkan sertifikasi gratis hanya dalam 25 hari

1. Ikuti kursus Proyek JavaScript ini untuk beralih dari pemula JS hingga membangun proyek Anda sendiri dengan percaya diri
2. Ikuti bootcamp wawancara coding ini jika Anda serius ingin dipekerjakan dan tidak memiliki gelar CS
3. Ikuti Kursus JavaScript Tingkat Lanjut ini untuk mempelajari konsep JS tingkat lanjut dan menjadi pengembang JS teratas

Pertanyaan Wawancara JavaScript. Pertanyaan dan Jawaban Wawancara JavaScript Teratas

Daftar isi

1. Apa cara yang mungkin untuk membuat objek dalam JavaScript

   There are many ways to create objects in javascript as below

   1. Object constructor

      The simplest way to create an empty object is using the Object constructor. Currently this approach is not recommended

      var object = new Object();

   2. Object's create method

      The create method of Object creates a new object by passing the prototype object as a parameter

      var object = Object.create(null);

   3. Object literal syntax

      The object literal syntax (or object initializer), is a comma-separated set of name-value pairs wrapped in curly braces

      var object = {
           name: "Sudheer",
           age: 34
      };
      
      Object literal property values can be of any data type, including array, function, and nested object.

      Note. This is an easiest way to create an object

   4. Function constructor

      Create any function and apply the new operator to create object instances,

      function Person(name) {
        this.name = name;
        this.age = 21;
      }
      var object = new Person("Sudheer");

   5. Function constructor with prototype

      This is similar to function constructor but it uses prototype for their properties and methods,

      function Person() {}
      Person.prototype.name = "Sudheer";
      var object = new Person();

      This is equivalent to an instance created with an object create method with a function prototype and then call that function with an instance and parameters as arguments

      function func() {};
      
      new func(x, y, z);

      (OR)

      // Create a new instance using function prototype.
      var newInstance = Object.create(func.prototype)
      
      // Call the function
      var result = func.call(newInstance, x, y, z),
      
      // If the result is a non-null object then use it otherwise just use the new instance.
      console.log(result && typeof result === 'object' ? result : newInstance);

   6. ES6 Class syntax

      ES6 introduces class feature to create the objects

      class Person {
        constructor(name) {
          this.name = name;
        }
      }
      
      var object = new Person("Sudheer");

   7. Singleton pattern

      A Singleton is an object which can only be instantiated one time. Repeated calls to its constructor return the same instance and this way one can ensure that they don't accidentally create multiple instances

      var object = new (function () {
        this.name = "Sudheer";
      })();

2. What is a prototype chain

   Prototype chaining is used to build new types of objects based on existing ones. It is similar to inheritance in a class based language

   The prototype on object instance is available through Object. getPrototypeOf(object) or __proto__ property whereas prototype on constructors function is available through Object. prototype

   

3. What is the difference between Call, Apply and Bind

   Perbedaan antara Call, Apply dan Bind dapat dijelaskan dengan contoh di bawah ini,

   Call. The call() method invokes a function with a given

   function func() {};
   
   new func(x, y, z);

   48 value and arguments provided one by one

   var employee1 = { firstName: "John", lastName: "Rodson" };
   var employee2 = { firstName: "Jimmy", lastName: "Baily" };
   
   function invite(greeting1, greeting2) {
     console.log(
       greeting1 + " " + this.firstName + " " + this.lastName + ", " + greeting2
     );
   }
   
   invite.call(employee1, "Hello", "How are you?"); // Hello John Rodson, How are you?
   invite.call(employee2, "Hello", "How are you?"); // Hello Jimmy Baily, How are you?

   Apply. Invokes the function with a given

   function func() {};
   
   new func(x, y, z);

   48 value and allows you to pass in arguments as an array

   var object = Object.create(null);

   0

   mengikat. mengembalikan fungsi baru, memungkinkan Anda untuk memberikan sejumlah argumen

   var object = Object.create(null);

   _1

   Panggilan dan lamaran cukup dipertukarkan. Keduanya segera menjalankan fungsi saat ini. Anda perlu memutuskan apakah lebih mudah mengirim dalam array atau daftar argumen yang dipisahkan koma. Anda dapat mengingat dengan memperlakukan Call untuk koma (daftar terpisah) dan Apply untuk Array

   Sedangkan Bind membuat fungsi baru yang

   function func() {};
   
   new func(x, y, z);

   48 disetel ke parameter pertama yang diteruskan ke bind()

4. Apa itu JSON dan operasi umumnya

   JSON adalah format data berbasis teks yang mengikuti sintaks objek JavaScript, yang dipopulerkan oleh

   function func() {};
   
   new func(x, y, z);

   51. Ini berguna ketika Anda ingin mengirimkan data melalui jaringan dan pada dasarnya hanya berupa file teks dengan ekstensi. json, and a MIME type of application/json

   Parsing. Converting a string to a native object

   var object = Object.create(null);

   2

   Stringification. converting a native object to a string so it can be transmitted across the network

   var object = Object.create(null);

   3

5. What is the purpose of the array slice method

   The slice() method returns the selected elements in an array as a new array object. It selects the elements starting at the given start argument, and ends at the given optional end argument without including the last element. If you omit the second argument then it selects till the end

   Some of the examples of this method are,

   var object = Object.create(null);

   4

   Note. Slice method won't mutate the original array but it returns the subset as a new array

6. What is the purpose of the array splice method

   The splice() method is used either adds/removes items to/from an array, and then returns the removed item. The first argument specifies the array position for insertion or deletion whereas the optional second argument indicates the number of elements to be deleted. Each additional argument is added to the array

   Some of the examples of this method are,

   var object = Object.create(null);

   5

   Note. Splice method modifies the original array and returns the deleted array

7. What is the difference between slice and splice

   Some of the major difference in a tabular form

   SliceSpliceDoesn't modify the original array(immutable)Modifies the original array(mutable)Returns the subset of original arrayReturns the deleted elements as arrayUsed to pick the elements from arrayUsed to insert or delete elements to/from array

8. How do you compare Object and Map

   Objects are similar to Maps in that both let you set keys to values, retrieve those values, delete keys, and detect whether something is stored at a key. Due to this reason, Objects have been used as Maps historically. But there are important differences that make using a Map preferable in certain cases

   1. The keys of an Object are Strings and Symbols, whereas they can be any value for a Map, including functions, objects, and any primitive
   2. The keys in Map are ordered while keys added to Object are not. Thus, when iterating over it, a Map object returns keys in order of insertion
   3. You can get the size of a Map easily with the size property, while the number of properties in an Object must be determined manually
   4. A Map is an iterable and can thus be directly iterated, whereas iterating over an Object requires obtaining its keys in some fashion and iterating over them
   5. An Object has a prototype, so there are default keys in the map that could collide with your keys if you're not careful. As of ES5 this can be bypassed by using map = Object. create(null), but this is seldom done
   6. A Map may perform better in scenarios involving frequent addition and removal of key pairs

9. Apa perbedaan antara operator == dan ===

   JavaScript provides both strict(===, . ==) and type-converting(==, . =) equality comparison. The strict operators take type of variable in consideration, while non-strict operators make type correction/conversion based upon values of variables. The strict operators follow the below conditions for different types,

   1. Two strings are strictly equal when they have the same sequence of characters, same length, and same characters in corresponding positions
   2. Two numbers are strictly equal when they are numerically equal. i. e, Having the same number value. There are two special cases in this,
      1. NaN is not equal to anything, including NaN
      2. Positive and negative zeros are equal to one another
   3. Two Boolean operands are strictly equal if both are true or both are false
   4. Two objects are strictly equal if they refer to the same Object
   5. Null and Undefined types are not equal with ===, but equal with ==. i. e, null===undefined --> false but null==undefined --> true

   Some of the example which covers the above cases,

   var object = Object.create(null);

   6

10. What are lambda or arrow functions

    An arrow function is a shorter syntax for a function expression and does not have its own this, arguments, super, or new. target. These functions are best suited for non-method functions, and they cannot be used as constructors

11. What is a first class function

    In Javascript, functions are first class objects. First-class functions means when functions in that language are treated like any other variable

    For example, in such a language, a function can be passed as an argument to other functions, can be returned by another function and can be assigned as a value to a variable. For example, in the below example, handler functions assigned to a listener

    var object = Object.create(null);

    7

12. What is a first order function

    First-order function is a function that doesn’t accept another function as an argument and doesn’t return a function as its return value

    var object = Object.create(null);

    8

13. What is a higher order function

    Higher-order function is a function that accepts another function as an argument or returns a function as a return value or both

    var object = Object.create(null);

    9

14. What is a unary function

    Unary function (i. e. monadic) is a function that accepts exactly one argument. It stands for a single argument accepted by a function

    Let us take an example of unary function,

    var object = {
         name: "Sudheer",
         age: 34
    };
    
    Object literal property values can be of any data type, including array, function, and nested object.

    0

15. What is the currying function

    Currying is the process of taking a function with multiple arguments and turning it into a sequence of functions each with only a single argument. Currying is named after a mathematician Haskell Curry. By applying currying, a n-ary function turns it into a unary function

    Let's take an example of n-ary function and how it turns into a currying function,

    var object = {
         name: "Sudheer",
         age: 34
    };
    
    Object literal property values can be of any data type, including array, function, and nested object.

    1

    Curried functions are great to improve code reusability and functional composition

16. What is a pure function

    A Pure function is a function where the return value is only determined by its arguments without any side effects. i. e, If you call a function with the same arguments 'n' number of times and 'n' number of places in the application then it will always return the same value

    Let's take an example to see the difference between pure and impure functions,

    var object = {
         name: "Sudheer",
         age: 34
    };
    
    Object literal property values can be of any data type, including array, function, and nested object.

    2

    As per the above code snippets, the Push function is impure itself by altering the array and returning a push number index independent of the parameter value. . Whereas Concat on the other hand takes the array and concatenates it with the other array producing a whole new array without side effects. Also, the return value is a concatenation of the previous array

    Remember that Pure functions are important as they simplify unit testing without any side effects and no need for dependency injection. They also avoid tight coupling and make it harder to break your application by not having any side effects. These principles are coming together with Immutability concept of ES6 by giving preference to const over let usage

17. What is the purpose of the let keyword

    The

    function func() {};
    
    new func(x, y, z);

    52 statement declares a block scope local variable. Hence the variables defined with let keyword are limited in scope to the block, statement, or expression on which it is used. Whereas variables declared with the

    function func() {};
    
    new func(x, y, z);

    53 keyword used to define a variable globally, or locally to an entire function regardless of block scope

    Let's take an example to demonstrate the usage,

    var object = {
         name: "Sudheer",
         age: 34
    };
    
    Object literal property values can be of any data type, including array, function, and nested object.

    _3

18. What is the difference between let and var

    Anda dapat membuat daftar perbedaan dalam format tabel

    varletIt is been available from the beginning of JavaScriptIntroduced as part of ES6It has function scopeIt has block scopeVariables will be hoistedHoisted but not initialized

    Let's take an example to see the difference,

    var object = {
         name: "Sudheer",
         age: 34
    };
    
    Object literal property values can be of any data type, including array, function, and nested object.

    4

19. What is the reason to choose the name let as a keyword

    function func() {};
    
    new func(x, y, z);

    52 is a mathematical statement that was adopted by early programming languages like Scheme and Basic. It has been borrowed from dozens of other languages that use

    function func() {};
    
    new func(x, y, z);

    52 already as a traditional keyword as close to

    function func() {};
    
    new func(x, y, z);

    53 as possible

20. How do you redeclare variables in switch block without an error

    Jika Anda mencoba untuk mendeklarasikan ulang variabel di

    function func() {};
    
    new func(x, y, z);

    57 maka akan menyebabkan kesalahan karena hanya ada satu blok. Misalnya, blok kode di bawah ini memunculkan kesalahan sintaksis seperti di bawah ini,

    var object = {
         name: "Sudheer",
         age: 34
    };
    
    Object literal property values can be of any data type, including array, function, and nested object.

    5

    To avoid this error, you can create a nested block inside a case clause and create a new block scoped lexical environment

    var object = {
         name: "Sudheer",
         age: 34
    };
    
    Object literal property values can be of any data type, including array, function, and nested object.

    6

21. What is the Temporal Dead Zone

    The Temporal Dead Zone is a behavior in JavaScript that occurs when declaring a variable with the let and const keywords, but not with var. In ECMAScript 6, accessing a

    function func() {};
    
    new func(x, y, z);

    52 or

    function func() {};
    
    new func(x, y, z);

    59 variable before its declaration (within its scope) causes a ReferenceError. The time span when that happens, between the creation of a variable’s binding and its declaration, is called the temporal dead zone

    Let's see this behavior with an example,

    var object = {
         name: "Sudheer",
         age: 34
    };
    
    Object literal property values can be of any data type, including array, function, and nested object.

    7

22. What is IIFE(Immediately Invoked Function Expression)

    IIFE (Immediately Invoked Function Expression) is a JavaScript function that runs as soon as it is defined. The signature of it would be as below,

    var object = {
         name: "Sudheer",
         age: 34
    };
    
    Object literal property values can be of any data type, including array, function, and nested object.

    8

    The primary reason to use an IIFE is to obtain data privacy because any variables declared within the IIFE cannot be accessed by the outside world. i. e, If you try to access variables with IIFE then it throws an error as below,

    var object = {
         name: "Sudheer",
         age: 34
    };
    
    Object literal property values can be of any data type, including array, function, and nested object.

    9

23. How do you decode or encode a URL in JavaScript?

    function func() {};
    
    new func(x, y, z);

    60 function is used to encode an URL. This function requires a URL string as a parameter and return that encoded string.

    function func() {};
    
    new func(x, y, z);

    61 function is used to decode an URL. This function requires an encoded URL string as parameter and return that decoded string

    Note. If you want to encode characters such as

    function func() {};
    
    new func(x, y, z);

    62 then you need to use

    function func() {};
    
    new func(x, y, z);

    63

    function Person(name) {
      this.name = name;
      this.age = 21;
    }
    var object = new Person("Sudheer");

    0

24. What is memoization

    Memoization is a programming technique which attempts to increase a function’s performance by caching its previously computed results. Each time a memoized function is called, its parameters are used to index the cache. If the data is present, then it can be returned, without executing the entire function. Jika tidak, fungsi dijalankan dan hasilnya ditambahkan ke cache. Let's take an example of adding function with memoization,

    function Person(name) {
      this.name = name;
      this.age = 21;
    }
    var object = new Person("Sudheer");

    1

25. What is Hoisting

    Hoisting is a JavaScript mechanism where variables, function declarations and classes are moved to the top of their scope before code execution. Remember that JavaScript only hoists declarations, not initialisation. Let's take a simple example of variable hoisting,

    function Person(name) {
      this.name = name;
      this.age = 21;
    }
    var object = new Person("Sudheer");

    2

    The above code looks like as below to the interpreter,

    function Person(name) {
      this.name = name;
      this.age = 21;
    }
    var object = new Person("Sudheer");

    3

    In the same fashion, function declarations are hoisted too

    function Person(name) {
      this.name = name;
      this.age = 21;
    }
    var object = new Person("Sudheer");

    4

    This hoisting makes functions to be safely used in code before they are declared

26. What are classes in ES6

    In ES6, Javascript classes are primarily syntactic sugar over JavaScript’s existing prototype-based inheritance. For example, the prototype based inheritance written in function expression as below,

    function Person(name) {
      this.name = name;
      this.age = 21;
    }
    var object = new Person("Sudheer");

    5

    Whereas ES6 classes can be defined as an alternative

    function Person(name) {
      this.name = name;
      this.age = 21;
    }
    var object = new Person("Sudheer");

    6

27. What are closures

    A closure is the combination of a function and the lexical environment within which that function was declared. i. e, It is an inner function that has access to the outer or enclosing function’s variables. The closure has three scope chains

    1. Own scope where variables defined between its curly brackets
    2. Outer function’s variables
    3. Global variables

    Let's take an example of closure concept,

    function Person(name) {
      this.name = name;
      this.age = 21;
    }
    var object = new Person("Sudheer");

    7

    As per the above code, the inner function(i. e, greetingInfo) has access to the variables in the outer function scope(i. e, Welcome) even after the outer function has returned

28. What are modules

    Modules refer to small units of independent, reusable code and also act as the foundation of many JavaScript design patterns. Most of the JavaScript modules export an object literal, a function, or a constructor

29. Why do you need modules

    Below are the list of benefits using modules in javascript ecosystem

    1. Maintainability
    2. Reusability
    3. Namespacing

30. What is scope in javascript

    Scope is the accessibility of variables, functions, and objects in some particular part of your code during runtime. In other words, scope determines the visibility of variables and other resources in areas of your code

31. What is a service worker

    A Service worker is basically a script (JavaScript file) that runs in the background, separate from a web page and provides features that don't need a web page or user interaction. Some of the major features of service workers are Rich offline experiences(offline first web application development), periodic background syncs, push notifications, intercept and handle network requests and programmatically managing a cache of responses

32. How do you manipulate DOM using a service worker

    Service worker can't access the DOM directly. But it can communicate with the pages it controls by responding to messages sent via the

    function func() {};
    
    new func(x, y, z);

    64 interface, and those pages can manipulate the DOM

33. How do you reuse information across service worker restarts

    The problem with service worker is that it gets terminated when not in use, and restarted when it's next needed, so you cannot rely on global state within a service worker's

    function func() {};
    
    new func(x, y, z);

    65 and

    function func() {};
    
    new func(x, y, z);

    66 handlers. In this case, service workers will have access to IndexedDB API in order to persist and reuse across restarts

34. What is IndexedDB

    IndexedDB is a low-level API for client-side storage of larger amounts of structured data, including files/blobs. This API uses indexes to enable high-performance searches of this data

35. What is web storage

    Penyimpanan web adalah API yang menyediakan mekanisme di mana browser dapat menyimpan pasangan kunci/nilai secara lokal di dalam browser pengguna, dengan cara yang jauh lebih intuitif daripada menggunakan cookie. The web storage provides two mechanisms for storing data on the client

    1. Local storage. It stores data for current origin with no expiration date
    2. Session storage. It stores data for one session and the data is lost when the browser tab is closed

36. What is a post message

    Post message is a method that enables cross-origin communication between Window objects. (i. e, between a page and a pop-up that it spawned, or between a page and an iframe embedded within it). Generally, scripts on different pages are allowed to access each other if and only if the pages follow same-origin policy(i. e, pages share the same protocol, port number, and host)

37. What is a Cookie

    A cookie is a piece of data that is stored on your computer to be accessed by your browser. Cookie disimpan sebagai pasangan kunci/nilai. For example, you can create a cookie named username as below,

    function Person(name) {
      this.name = name;
      this.age = 21;
    }
    var object = new Person("Sudheer");

    8
    

38. Why do you need a Cookie

    Cookies are used to remember information about the user profile(such as username). It basically involves two steps,

    1. When a user visits a web page, the user profile can be stored in a cookie
    2. Next time the user visits the page, the cookie remembers the user profile

39. What are the options in a cookie

    There are few below options available for a cookie,

    1. By default, the cookie is deleted when the browser is closed but you can change this behavior by setting expiry date (in UTC time)

    function Person(name) {
      this.name = name;
      this.age = 21;
    }
    var object = new Person("Sudheer");

    _9
    1. Secara default, cookie milik halaman saat ini. But you can tell the browser what path the cookie belongs to using a path parameter

    function Person() {}
    Person.prototype.name = "Sudheer";
    var object = new Person();

    0

40. How do you delete a cookie

    You can delete a cookie by setting the expiry date as a passed date. You don't need to specify a cookie value in this case. For example, you can delete a username cookie in the current page as below

    function Person() {}
    Person.prototype.name = "Sudheer";
    var object = new Person();

    1

    Note. You should define the cookie path option to ensure that you delete the right cookie. Some browsers doesn't allow to delete a cookie unless you specify a path parameter

41. What are the differences between cookie, local storage and session storage

    Below are some of the differences between cookie, local storage and session storage,

    FeatureCookieLocal storageSession storageAccessed on client or server sideBoth server-side & client-sideclient-side onlyclient-side onlyLifetimeAs configured using Expires optionuntil deleteduntil tab is closedSSL supportSupportedNot supportedNot supportedMaximum data size4KB5 MB5MB

42. What is the main difference between localStorage and sessionStorage

    LocalStorage is the same as SessionStorage but it persists the data even when the browser is closed and reopened(i. e it has no expiration time) whereas in sessionStorage data gets cleared when the page session ends

43. How do you access web storage

    The Window object implements the

    function func() {};
    
    new func(x, y, z);

    67 and

    function func() {};
    
    new func(x, y, z);

    68 objects which has

    function func() {};
    
    new func(x, y, z);

    69(window. localStorage) and

    function func() {};
    
    new func(x, y, z);

    70(window. sessionStorage) properties respectively. These properties create an instance of the Storage object, through which data items can be set, retrieved and removed for a specific domain and storage type (session or local). For example, you can read and write on local storage objects as below

    function Person() {}
    Person.prototype.name = "Sudheer";
    var object = new Person();

    2

44. What are the methods available on session storage

    The session storage provided methods for reading, writing and clearing the session data

    function Person() {}
    Person.prototype.name = "Sudheer";
    var object = new Person();

    3

45. What is a storage event and its event handler

    The StorageEvent is an event that fires when a storage area has been changed in the context of another document. Sedangkan properti onstorage adalah EventHandler untuk memproses peristiwa penyimpanan. Sintaksnya akan seperti di bawah ini

    function Person() {}
    Person.prototype.name = "Sudheer";
    var object = new Person();

    4

    Let's take the example usage of onstorage event handler which logs the storage key and it's values

    function Person() {}
    Person.prototype.name = "Sudheer";
    var object = new Person();

    5

46. Why do you need web storage

    Web storage is more secure, and large amounts of data can be stored locally, without affecting website performance. Also, the information is never transferred to the server. Hence this is a more recommended approach than Cookies

47. How do you check web storage browser support

    You need to check browser support for localStorage and sessionStorage before using web storage,

    function Person() {}
    Person.prototype.name = "Sudheer";
    var object = new Person();

    6

48. How do you check web workers browser support

    You need to check browser support for web workers before using it

    function Person() {}
    Person.prototype.name = "Sudheer";
    var object = new Person();

    7

49. Give an example of a web worker

    You need to follow below steps to start using web workers for counting example

    1. Create a Web Worker File. You need to write a script to increment the count value. Let's name it as counter. js

    function Person() {}
    Person.prototype.name = "Sudheer";
    var object = new Person();

    8

    Here postMessage() method is used to post a message back to the HTML page

    1. Create a Web Worker Object. You can create a web worker object by checking for browser support. Let's name this file as web_worker_example. js

    function Person() {}
    Person.prototype.name = "Sudheer";
    var object = new Person();

    9

    and we can receive messages from web worker

    function func() {};
    
    new func(x, y, z);

    0
    1. Terminate a Web Worker. Web workers will continue to listen for messages (even after the external script is finished) until it is terminated. You can use the terminate() method to terminate listening to the messages

    function func() {};
    
    new func(x, y, z);

    1
    1. Reuse the Web Worker. If you set the worker variable to undefined you can reuse the code

    function func() {};
    
    new func(x, y, z);

    2

50. What are the restrictions of web workers on DOM

    WebWorkers don't have access to below javascript objects since they are defined in an external files

    1. Window object
    2. Document object
    3. Parent object

51. What is a promise

    A promise is an object that may produce a single value some time in the future with either a resolved value or a reason that it’s not resolved(for example, network error). It will be in one of the 3 possible states. fulfilled, rejected, or pending

    The syntax of Promise creation looks like below,

    function func() {};
    
    new func(x, y, z);

    3

    The usage of a promise would be as below,

    function func() {};
    
    new func(x, y, z);

    4

    The action flow of a promise will be as below,

    

52. Why do you need a promise

    Promises are used to handle asynchronous operations. They provide an alternative approach for callbacks by reducing the callback hell and writing the cleaner code

53. What are the three states of promise

    Janji memiliki tiga keadaan

    1. Pending. This is an initial state of the Promise before an operation begins
    2. Fulfilled. This state indicates that the specified operation was completed
    3. Rejected. This state indicates that the operation did not complete. In this case an error value will be thrown

54. What is a callback function

    A callback function is a function passed into another function as an argument. This function is invoked inside the outer function to complete an action. Let's take a simple example of how to use callback function

    function func() {};
    
    new func(x, y, z);

    5

55. Why do we need callbacks

    The callbacks are needed because javascript is an event driven language. That means instead of waiting for a response javascript will keep executing while listening for other events. Mari kita ambil contoh dengan fungsi pertama yang memanggil panggilan API (disimulasikan oleh setTimeout) dan fungsi selanjutnya yang mencatat pesan

    function func() {};
    
    new func(x, y, z);

    _6

    As observed from the output, javascript didn't wait for the response of the first function and the remaining code block got executed. Jadi callback digunakan untuk memastikan bahwa kode tertentu tidak dijalankan sampai kode lain selesai dieksekusi

56. What is a callback hell

    Callback Hell is an anti-pattern with multiple nested callbacks which makes code hard to read and debug when dealing with asynchronous logic. The callback hell looks like below,

    function func() {};
    
    new func(x, y, z);

    7

57. What are server-sent events

    Server-sent events (SSE) is a server push technology enabling a browser to receive automatic updates from a server via HTTP connection without resorting to polling. These are a one way communications channel - events flow from server to client only. Ini telah digunakan dalam pembaruan Facebook/Twitter, pembaruan harga saham, umpan berita, dll

58. Bagaimana Anda menerima pemberitahuan acara yang dikirim server

    Objek EventSource digunakan untuk menerima notifikasi event yang dikirim server. Misalnya, Anda dapat menerima pesan dari server seperti di bawah ini,

    function func() {};
    
    new func(x, y, z);

    _8

59. Bagaimana Anda memeriksa dukungan browser untuk acara yang dikirim server

    Anda dapat melakukan dukungan browser untuk acara yang dikirim server sebelum menggunakannya seperti di bawah ini,

    function func() {};
    
    new func(x, y, z);

    _9

60. Apa saja acara yang tersedia untuk acara yang dikirim server

    Di bawah ini adalah daftar acara yang tersedia untuk acara yang dikirim server

    EventDescriptiononopenDigunakan ketika koneksi ke server dibuka pada pesanKejadian ini digunakan ketika pesan diterima pada kesalahanTerjadi ketika terjadi kesalahan

61. Apa aturan utama janji

    Janji harus mengikuti seperangkat aturan tertentu,

    1. Janji adalah objek yang memasok metode ________5______71 yang sesuai standar
    2. Janji yang tertunda dapat beralih ke status dipenuhi atau ditolak
    3. Janji yang dipenuhi atau ditolak diselesaikan dan tidak boleh beralih ke keadaan lain mana pun
    4. Setelah janji diselesaikan, nilainya tidak boleh berubah

62. Apa itu panggilan balik dalam panggilan balik

    Anda dapat menyarangkan satu panggilan balik di dalam panggilan balik lain untuk menjalankan tindakan secara berurutan satu per satu. Ini dikenal sebagai panggilan balik dalam panggilan balik

    // Create a new instance using function prototype.
    var newInstance = Object.create(func.prototype)
    
    // Call the function
    var result = func.call(newInstance, x, y, z),
    
    // If the result is a non-null object then use it otherwise just use the new instance.
    console.log(result && typeof result === 'object' ? result : newInstance);

    _0

63. Apa itu rantai janji

    Proses mengeksekusi urutan tugas asinkron satu demi satu menggunakan janji dikenal sebagai rantai Janji. Mari kita ambil contoh dari promise chaining untuk menghitung hasil akhir,

    // Create a new instance using function prototype.
    var newInstance = Object.create(func.prototype)
    
    // Call the function
    var result = func.call(newInstance, x, y, z),
    
    // If the result is a non-null object then use it otherwise just use the new instance.
    console.log(result && typeof result === 'object' ? result : newInstance);

    _1

    Pada penangan di atas, hasilnya diteruskan ke rantai. kemudian() penangan dengan alur kerja di bawah ini,

    1. Janji awal selesai dalam 1 detik,
    2. Setelah itu

       function func() {};
       
       new func(x, y, z);

       _72 handler dipanggil dengan mencatat hasil (1) dan kemudian mengembalikan janji dengan nilai hasil * 2
    3. Setelah itu nilai diteruskan ke penangan

       function func() {};
       
       new func(x, y, z);

       _72 berikutnya dengan mencatat hasil (2) dan mengembalikan janji dengan hasil * 3
    4. Akhirnya nilai diteruskan ke penangan

       function func() {};
       
       new func(x, y, z);

       _72 terakhir dengan mencatat hasil (6) dan mengembalikan janji dengan hasil * 4

64. Apa itu janji. semua

    Janji. all adalah janji yang mengambil serangkaian janji sebagai input (dapat diubah), dan itu diselesaikan ketika semua janji diselesaikan atau salah satu dari janji itu ditolak. Misalnya, sintaks janji. semua metode di bawah ini,

    // Create a new instance using function prototype.
    var newInstance = Object.create(func.prototype)
    
    // Call the function
    var result = func.call(newInstance, x, y, z),
    
    // If the result is a non-null object then use it otherwise just use the new instance.
    console.log(result && typeof result === 'object' ? result : newInstance);

    _2

    Catatan. Ingatlah bahwa urutan janji (menghasilkan hasilnya) dipertahankan sesuai urutan input

65. Apa tujuan dari metode balapan yang dijanjikan

    Janji. race() metode akan mengembalikan instance janji yang pertama kali diselesaikan atau ditolak. Let's take an example of race() method where promise2 is resolved first

    // Create a new instance using function prototype.
    var newInstance = Object.create(func.prototype)
    
    // Call the function
    var result = func.call(newInstance, x, y, z),
    
    // If the result is a non-null object then use it otherwise just use the new instance.
    console.log(result && typeof result === 'object' ? result : newInstance);

    3

66. What is a strict mode in javascript

    Strict Mode is a new feature in ECMAScript 5 that allows you to place a program, or a function, in a “strict” operating context. This way it prevents certain actions from being taken and throws more exceptions. The literal expression

    function func() {};
    
    new func(x, y, z);

    75 instructs the browser to use the javascript code in the Strict mode

67. Why do you need strict mode

    Strict mode is useful to write "secure" JavaScript by notifying "bad syntax" into real errors. For example, it eliminates accidentally creating a global variable by throwing an error and also throws an error for assignment to a non-writable property, a getter-only property, a non-existing property, a non-existing variable, or a non-existing object

68. How do you declare strict mode

    The strict mode is declared by adding "use strict"; to the beginning of a script or a function. If declared at the beginning of a script, it has global scope

    // Create a new instance using function prototype.
    var newInstance = Object.create(func.prototype)
    
    // Call the function
    var result = func.call(newInstance, x, y, z),
    
    // If the result is a non-null object then use it otherwise just use the new instance.
    console.log(result && typeof result === 'object' ? result : newInstance);

    4

    and if you declare inside a function, it has local scope

    // Create a new instance using function prototype.
    var newInstance = Object.create(func.prototype)
    
    // Call the function
    var result = func.call(newInstance, x, y, z),
    
    // If the result is a non-null object then use it otherwise just use the new instance.
    console.log(result && typeof result === 'object' ? result : newInstance);

    5

69. What is the purpose of double exclamation

    The double exclamation or negation(. ) ensures the resulting type is a boolean. If it was falsey (e. g. 0, null, undefined, etc. ), it will be false, otherwise, true. For example, you can test IE version using this expression as below,

    // Create a new instance using function prototype.
    var newInstance = Object.create(func.prototype)
    
    // Call the function
    var result = func.call(newInstance, x, y, z),
    
    // If the result is a non-null object then use it otherwise just use the new instance.
    console.log(result && typeof result === 'object' ? result : newInstance);

    6

    If you don't use this expression then it returns the original value

    // Create a new instance using function prototype.
    var newInstance = Object.create(func.prototype)
    
    // Call the function
    var result = func.call(newInstance, x, y, z),
    
    // If the result is a non-null object then use it otherwise just use the new instance.
    console.log(result && typeof result === 'object' ? result : newInstance);

    7

    Note. The expression . is not an operator, but it is just twice of . operator

70. What is the purpose of the delete operator

    The delete keyword is used to delete the property as well as its value

    // Create a new instance using function prototype.
    var newInstance = Object.create(func.prototype)
    
    // Call the function
    var result = func.call(newInstance, x, y, z),
    
    // If the result is a non-null object then use it otherwise just use the new instance.
    console.log(result && typeof result === 'object' ? result : newInstance);

    8

71. What is typeof operator

    You can use the JavaScript typeof operator to find the type of a JavaScript variable. It returns the type of a variable or an expression

    // Create a new instance using function prototype.
    var newInstance = Object.create(func.prototype)
    
    // Call the function
    var result = func.call(newInstance, x, y, z),
    
    // If the result is a non-null object then use it otherwise just use the new instance.
    console.log(result && typeof result === 'object' ? result : newInstance);

    9

72. What is undefined property

    The undefined property indicates that a variable has not been assigned a value, or declared but not initialized at all. The type of undefined value is undefined too

    class Person {
      constructor(name) {
        this.name = name;
      }
    }
    
    var object = new Person("Sudheer");

    0

    Any variable can be emptied by setting the value to undefined

    class Person {
      constructor(name) {
        this.name = name;
      }
    }
    
    var object = new Person("Sudheer");

    1

73. What is null value

    The value null represents the intentional absence of any object value. Ini adalah salah satu nilai primitif JavaScript. The type of null value is object. You can empty the variable by setting the value to null

    class Person {
      constructor(name) {
        this.name = name;
      }
    }
    
    var object = new Person("Sudheer");

    2

74. What is the difference between null and undefined

    Below are the main differences between null and undefined,

    NullUndefinedIt is an assignment value which indicates that variable points to no object. It is not an assignment value where a variable has been declared but has not yet been assigned a value. Type of null is objectType of undefined is undefinedThe null value is a primitive value that represents the null, empty, or non-existent reference. The undefined value is a primitive value used when a variable has not been assigned a value. Indicates the absence of a value for a variableIndicates absence of variable itselfConverted to zero (0) while performing primitive operationsConverted to NaN while performing primitive operations

75. What is eval

    The eval() function evaluates JavaScript code represented as a string. The string can be a JavaScript expression, variable, statement, or sequence of statements

    class Person {
      constructor(name) {
        this.name = name;
      }
    }
    
    var object = new Person("Sudheer");

    3

76. What is the difference between window and document

    Below are the main differences between window and document,

    WindowDocumentIt is the root level element in any web pageIt is the direct child of the window object. This is also known as Document Object Model(DOM)By default window object is available implicitly in the pageYou can access it via window. document or document. It has methods like alert(), confirm() and properties like document, locationIt provides methods like getElementById, getElementsByTagName, createElement etc

77. Bagaimana Anda mengakses riwayat dalam javascript

    The window. history object contains the browser's history. You can load previous and next URLs in the history using back() and next() methods

    class Person {
      constructor(name) {
        this.name = name;
      }
    }
    
    var object = new Person("Sudheer");

    4

    Note. You can also access history without window prefix

78. Bagaimana Anda mendeteksi tombol caps lock dihidupkan atau tidak

    The

    function func() {};
    
    new func(x, y, z);

    76 is used to return a boolean value that indicates whether the specified modifier key is activated or not. The modifiers such as CapsLock, ScrollLock and NumLock are activated when they are clicked, and deactivated when they are clicked again

    Let's take an input element to detect the CapsLock on/off behavior with an example,

    class Person {
      constructor(name) {
        this.name = name;
      }
    }
    
    var object = new Person("Sudheer");

    5

79. What is isNaN

    The isNaN() function is used to determine whether a value is an illegal number (Not-a-Number) or not. i. e, This function returns true if the value equates to NaN. Otherwise it returns false

    class Person {
      constructor(name) {
        this.name = name;
      }
    }
    
    var object = new Person("Sudheer");

    6

80. What are the differences between undeclared and undefined variables

    Below are the major differences between undeclared(not defined) and undefined variables,

    undeclaredundefinedThese variables do not exist in a program and are not declaredThese variables declared in the program but have not assigned any valueIf you try to read the value of an undeclared variable, then a runtime error is encounteredIf you try to read the value of an undefined variable, an undefined value is returned

81. What are global variables

    Global variables are those that are available throughout the length of the code without any scope. The var keyword is used to declare a local variable but if you omit it then it will become global variable

    class Person {
      constructor(name) {
        this.name = name;
      }
    }
    
    var object = new Person("Sudheer");

    7

82. What are the problems with global variables

    The problem with global variables is the conflict of variable names of local and global scope. It is also difficult to debug and test the code that relies on global variables

83. What is NaN property

    The NaN property is a global property that represents "Not-a-Number" value. i. e, It indicates that a value is not a legal number. It is very rare to use NaN in a program but it can be used as return value for few cases

    class Person {
      constructor(name) {
        this.name = name;
      }
    }
    
    var object = new Person("Sudheer");

    8

84. Apa tujuan dari fungsi isFinite

    The isFinite() function is used to determine whether a number is a finite, legal number. It returns false if the value is +infinity, -infinity, or NaN (Not-a-Number), otherwise it returns true

    class Person {
      constructor(name) {
        this.name = name;
      }
    }
    
    var object = new Person("Sudheer");

    9

85. What is an event flow

    Event flow is the order in which event is received on the web page. When you click an element that is nested in various other elements, before your click actually reaches its destination, or target element, it must trigger the click event for each of its parent elements first, starting at the top with the global window object. There are two ways of event flow

    1. Top to Bottom(Event Capturing)
    2. Bottom to Top (Event Bubbling)

86. What is event bubbling

    Event bubbling is a type of event propagation where the event first triggers on the innermost target element, and then successively triggers on the ancestors (parents) of the target element in the same nesting hierarchy till it reaches the outermost DOM element

87. What is event capturing

    Event capturing is a type of event propagation where the event is first captured by the outermost element, and then successively triggers on the descendants (children) of the target element in the same nesting hierarchy till it reaches the innermost DOM element

88. How do you submit a form using JavaScript

    You can submit a form using

    function func() {};
    
    new func(x, y, z);

    77. All the form input's information is submitted using onsubmit event handler

    var object = new (function () {
      this.name = "Sudheer";
    })();

    0

89. How do you find operating system details

    The window. navigator object contains information about the visitor's browser OS details. Some of the OS properties are available under platform property,

    var object = new (function () {
      this.name = "Sudheer";
    })();

    1

90. What is the difference between document load and DOMContentLoaded events

    The

    function func() {};
    
    new func(x, y, z);

    78 event is fired when the initial HTML document has been completely loaded and parsed, without waiting for assets(stylesheets, images, and subframes) to finish loading. Whereas The load event is fired when the whole page has loaded, including all dependent resources(stylesheets, images)

91. What is the difference between native, host and user objects

    function func() {};
    
    new func(x, y, z);

    79 are objects that are part of the JavaScript language defined by the ECMAScript specification. For example, String, Math, RegExp, Object, Function etc core objects defined in the ECMAScript spec.

    function func() {};
    
    new func(x, y, z);

    80 are objects provided by the browser or runtime environment (Node). For example, window, XmlHttpRequest, DOM nodes etc are considered as host objects.

    function func() {};
    
    new func(x, y, z);

    81 are objects defined in the javascript code. For example, User objects created for profile information

92. What are the tools or techniques used for debugging JavaScript code

    You can use below tools or techniques for debugging javascript

    1. Chrome Devtools
    2. debugger statement
    3. Good old console. log statement

93. What are the pros and cons of promises over callbacks

    Below are the list of pros and cons of promises over callbacks,

    Pros

    1. It avoids callback hell which is unreadable
    2. Easy to write sequential asynchronous code with . then()
    3. Easy to write parallel asynchronous code with Promise. all()
    4. Solves some of the common problems of callbacks(call the callback too late, too early, many times and swallow errors/exceptions)

    Cons

    1. It makes little complex code
    2. You need to load a polyfill if ES6 is not supported

94. What is the difference between an attribute and a property

    Attributes are defined on the HTML markup whereas properties are defined on the DOM. For example, the below HTML element has 2 attributes type and value,

    var object = new (function () {
      this.name = "Sudheer";
    })();

    2

    You can retrieve the attribute value as below,

    var object = new (function () {
      this.name = "Sudheer";
    })();

    _3

    And after you change the value of the text field to "Good evening", it becomes like

    var object = new (function () {
      this.name = "Sudheer";
    })();

    4

95. What is same-origin policy

    The same-origin policy is a policy that prevents JavaScript from making requests across domain boundaries. An origin is defined as a combination of URI scheme, hostname, and port number. If you enable this policy then it prevents a malicious script on one page from obtaining access to sensitive data on another web page using Document Object Model(DOM)

96. What is the purpose of void 0

    Void(0) is used to prevent the page from refreshing. This will be helpful to eliminate the unwanted side-effect, because it will return the undefined primitive value. It is commonly used for HTML documents that use href="JavaScript. Void(0);" within an

    function func() {};
    
    new func(x, y, z);

    82 element. i. e, when you click a link, the browser loads a new page or refreshes the same page. But this behavior will be prevented using this expression. For example, the below link notify the message without reloading the page

    var object = new (function () {
      this.name = "Sudheer";
    })();

    5

97. Is JavaScript a compiled or interpreted language

    JavaScript adalah bahasa yang ditafsirkan, bukan bahasa yang dikompilasi. An interpreter in the browser reads over the JavaScript code, interprets each line, and runs it. Saat ini browser modern menggunakan teknologi yang dikenal sebagai kompilasi Just-In-Time (JIT), yang mengkompilasi JavaScript menjadi bytecode yang dapat dieksekusi saat akan dijalankan.

98. Apakah JavaScript peka huruf besar-kecil

    Ya, JavaScript adalah bahasa yang peka terhadap huruf besar-kecil. Kata kunci bahasa, variabel, nama fungsi & objek, dan pengidentifikasi lainnya harus selalu diketik dengan kapitalisasi huruf yang konsisten

99. Apakah ada hubungan antara Java dan JavaScript

    No, they are entirely two different programming languages and have nothing to do with each other. Tetapi keduanya adalah bahasa Pemrograman Berorientasi Objek dan seperti banyak bahasa lainnya, mereka mengikuti sintaks yang sama untuk fitur dasar (jika, jika tidak, untuk, beralih, istirahat, lanjutkan dll)

100. Apa itu peristiwa

     Acara adalah "hal-hal" yang terjadi pada elemen HTML. Saat JavaScript digunakan di halaman HTML, JavaScript dapat

     function func() {};
     
     new func(x, y, z);

     83 pada peristiwa ini. Some of the examples of HTML events are,
     1. Web page has finished loading
     2. Input field was changed
     3. Button was clicked

     Let's describe the behavior of click event for button element,

     var object = new (function () {
       this.name = "Sudheer";
     })();

     6

101. Who created javascript

     JavaScript was created by Brendan Eich in 1995 during his time at Netscape Communications. Initially it was developed under the name

     function func() {};
     
     new func(x, y, z);

     84, but later the language was officially called

     function func() {};
     
     new func(x, y, z);

     85 when it first shipped in beta releases of Netscape

102. What is the use of preventDefault method

     The preventDefault() method cancels the event if it is cancelable, meaning that the default action or behaviour that belongs to the event will not occur. For example, prevent form submission when clicking on submit button and prevent opening the page URL when clicking on hyperlink are some common use cases

     var object = new (function () {
       this.name = "Sudheer";
     })();

     7

     Note. Remember that not all events are cancelable

103. What is the use of stopPropagation method

     The stopPropagation method is used to stop the event from bubbling up the event chain. For example, the below nested divs with stopPropagation method prevents default event propagation when clicking on nested div(Div1)

     var object = new (function () {
       this.name = "Sudheer";
     })();

     8

104. What are the steps involved in return false usage

     The return false statement in event handlers performs the below steps,

     1. First it stops the browser's default action or behaviour
     2. It prevents the event from propagating the DOM
     3. Stops callback execution and returns immediately when called

105. What is BOM

     The Browser Object Model (BOM) allows JavaScript to "talk to" the browser. Ini terdiri dari navigator objek, sejarah, layar, lokasi dan dokumen yang merupakan anak-anak dari jendela. The Browser Object Model is not standardized and can change based on different browsers

     

106. What is the use of setTimeout

     The setTimeout() method is used to call a function or evaluate an expression after a specified number of milliseconds. For example, let's log a message after 2 seconds using setTimeout method,

     var object = new (function () {
       this.name = "Sudheer";
     })();

     9

107. What is the use of setInterval

     The setInterval() method is used to call a function or evaluate an expression at specified intervals (in milliseconds). For example, let's log a message after 2 seconds using setInterval method,

     var employee1 = { firstName: "John", lastName: "Rodson" };
     var employee2 = { firstName: "Jimmy", lastName: "Baily" };
     
     function invite(greeting1, greeting2) {
       console.log(
         greeting1 + " " + this.firstName + " " + this.lastName + ", " + greeting2
       );
     }
     
     invite.call(employee1, "Hello", "How are you?"); // Hello John Rodson, How are you?
     invite.call(employee2, "Hello", "How are you?"); // Hello Jimmy Baily, How are you?

     0

108. Why is JavaScript treated as Single threaded

     JavaScript is a single-threaded language. Because the language specification does not allow the programmer to write code so that the interpreter can run parts of it in parallel in multiple threads or processes. Whereas languages like java, go, C++ can make multi-threaded and multi-process programs

109. What is an event delegation

     Event delegation is a technique for listening to events where you delegate a parent element as the listener for all of the events that happen inside it

     For example, if you wanted to detect field changes in inside a specific form, you can use event delegation technique,

     var employee1 = { firstName: "John", lastName: "Rodson" };
     var employee2 = { firstName: "Jimmy", lastName: "Baily" };
     
     function invite(greeting1, greeting2) {
       console.log(
         greeting1 + " " + this.firstName + " " + this.lastName + ", " + greeting2
       );
     }
     
     invite.call(employee1, "Hello", "How are you?"); // Hello John Rodson, How are you?
     invite.call(employee2, "Hello", "How are you?"); // Hello Jimmy Baily, How are you?

     1

110. What is ECMAScript

     ECMAScript is the scripting language that forms the basis of JavaScript. ECMAScript standardized by the ECMA International standards organization in the ECMA-262 and ECMA-402 specifications. The first edition of ECMAScript was released in 1997

111. What is JSON

     JSON (JavaScript Object Notation) is a lightweight format that is used for data interchanging. It is based on a subset of JavaScript language in the way objects are built in JavaScript

112. What are the syntax rules of JSON

     Below are the list of syntax rules of JSON

     1. The data is in name/value pairs
     2. The data is separated by commas
     3. Curly braces hold objects
     4. Square brackets hold arrays

113. What is the purpose JSON stringify

     When sending data to a web server, the data has to be in a string format. You can achieve this by converting JSON object into a string using stringify() method

     var employee1 = { firstName: "John", lastName: "Rodson" };
     var employee2 = { firstName: "Jimmy", lastName: "Baily" };
     
     function invite(greeting1, greeting2) {
       console.log(
         greeting1 + " " + this.firstName + " " + this.lastName + ", " + greeting2
       );
     }
     
     invite.call(employee1, "Hello", "How are you?"); // Hello John Rodson, How are you?
     invite.call(employee2, "Hello", "How are you?"); // Hello Jimmy Baily, How are you?

     2

114. How do you parse JSON string

     When receiving the data from a web server, the data is always in a string format. But you can convert this string value to a javascript object using parse() method

     var employee1 = { firstName: "John", lastName: "Rodson" };
     var employee2 = { firstName: "Jimmy", lastName: "Baily" };
     
     function invite(greeting1, greeting2) {
       console.log(
         greeting1 + " " + this.firstName + " " + this.lastName + ", " + greeting2
       );
     }
     
     invite.call(employee1, "Hello", "How are you?"); // Hello John Rodson, How are you?
     invite.call(employee2, "Hello", "How are you?"); // Hello Jimmy Baily, How are you?

     3

115. Why do you need JSON

     When exchanging data between a browser and a server, the data can only be text. Since JSON is text only, it can easily be sent to and from a server, and used as a data format by any programming language

116. What are PWAs

     Progressive web applications (PWAs) are a type of mobile app delivered through the web, built using common web technologies including HTML, CSS and JavaScript. These PWAs are deployed to servers, accessible through URLs, and indexed by search engines

117. What is the purpose of clearTimeout method

     The clearTimeout() function is used in javascript to clear the timeout which has been set by setTimeout()function before that. i. e, The return value of setTimeout() function is stored in a variable and it’s passed into the clearTimeout() function to clear the timer

     For example, the below setTimeout method is used to display the message after 3 seconds. This timeout can be cleared by the clearTimeout() method

     var employee1 = { firstName: "John", lastName: "Rodson" };
     var employee2 = { firstName: "Jimmy", lastName: "Baily" };
     
     function invite(greeting1, greeting2) {
       console.log(
         greeting1 + " " + this.firstName + " " + this.lastName + ", " + greeting2
       );
     }
     
     invite.call(employee1, "Hello", "How are you?"); // Hello John Rodson, How are you?
     invite.call(employee2, "Hello", "How are you?"); // Hello Jimmy Baily, How are you?

     4

118. What is the purpose of clearInterval method

     The clearInterval() function is used in javascript to clear the interval which has been set by setInterval() function. i. e, The return value returned by setInterval() function is stored in a variable and it’s passed into the clearInterval() function to clear the interval

     For example, the below setInterval method is used to display the message for every 3 seconds. This interval can be cleared by the clearInterval() method

     var employee1 = { firstName: "John", lastName: "Rodson" };
     var employee2 = { firstName: "Jimmy", lastName: "Baily" };
     
     function invite(greeting1, greeting2) {
       console.log(
         greeting1 + " " + this.firstName + " " + this.lastName + ", " + greeting2
       );
     }
     
     invite.call(employee1, "Hello", "How are you?"); // Hello John Rodson, How are you?
     invite.call(employee2, "Hello", "How are you?"); // Hello Jimmy Baily, How are you?

     5

119. How do you redirect new page in javascript

     In vanilla javascript, you can redirect to a new page using the

     function func() {};
     
     new func(x, y, z);

     86 property of window object. The syntax would be as follows,

     var employee1 = { firstName: "John", lastName: "Rodson" };
     var employee2 = { firstName: "Jimmy", lastName: "Baily" };
     
     function invite(greeting1, greeting2) {
       console.log(
         greeting1 + " " + this.firstName + " " + this.lastName + ", " + greeting2
       );
     }
     
     invite.call(employee1, "Hello", "How are you?"); // Hello John Rodson, How are you?
     invite.call(employee2, "Hello", "How are you?"); // Hello Jimmy Baily, How are you?

     6

120. How do you check whether a string contains a substring

     There are 3 possible ways to check whether a string contains a substring or not,

     1. Using includes. ES6 provided

        function func() {};
        
        new func(x, y, z);

        87 method to test a string contains a substring

     var employee1 = { firstName: "John", lastName: "Rodson" };
     var employee2 = { firstName: "Jimmy", lastName: "Baily" };
     
     function invite(greeting1, greeting2) {
       console.log(
         greeting1 + " " + this.firstName + " " + this.lastName + ", " + greeting2
       );
     }
     
     invite.call(employee1, "Hello", "How are you?"); // Hello John Rodson, How are you?
     invite.call(employee2, "Hello", "How are you?"); // Hello Jimmy Baily, How are you?

     7
     1. Menggunakan indexOf. In an ES5 or older environment, you can use

        function func() {};
        
        new func(x, y, z);

        88 which returns the index of a substring. If the index value is not equal to -1 then it means the substring exists in the main string

     var employee1 = { firstName: "John", lastName: "Rodson" };
     var employee2 = { firstName: "Jimmy", lastName: "Baily" };
     
     function invite(greeting1, greeting2) {
       console.log(
         greeting1 + " " + this.firstName + " " + this.lastName + ", " + greeting2
       );
     }
     
     invite.call(employee1, "Hello", "How are you?"); // Hello John Rodson, How are you?
     invite.call(employee2, "Hello", "How are you?"); // Hello Jimmy Baily, How are you?

     8
     1. Using RegEx. The advanced solution is using Regular expression's test method(

        function func() {};
        
        new func(x, y, z);

        89), which allows for testing for against regular expressions

     var employee1 = { firstName: "John", lastName: "Rodson" };
     var employee2 = { firstName: "Jimmy", lastName: "Baily" };
     
     function invite(greeting1, greeting2) {
       console.log(
         greeting1 + " " + this.firstName + " " + this.lastName + ", " + greeting2
       );
     }
     
     invite.call(employee1, "Hello", "How are you?"); // Hello John Rodson, How are you?
     invite.call(employee2, "Hello", "How are you?"); // Hello Jimmy Baily, How are you?

     9

121. How do you validate an email in javascript

     You can validate an email in javascript using regular expressions. It is recommended to do validations on the server side instead of the client side. Because the javascript can be disabled on the client side

     var object = Object.create(null);

     00

     The above regular expression accepts unicode characters

122. How do you get the current url with javascript

     You can use

     function func() {};
     
     new func(x, y, z);

     90 expression to get the current url path and you can use the same expression for updating the URL too. You can also use

     function func() {};
     
     new func(x, y, z);

     91 for read-only purposes but this solution has issues in FF

     var object = Object.create(null);

     01

123. What are the various url properties of location object

     The below

     function func() {};
     
     new func(x, y, z);

     92 object properties can be used to access URL components of the page,
     1. href - The entire URL
     2. protocol - The protocol of the URL
     3. host - The hostname and port of the URL
     4. hostname - The hostname of the URL
     5. port - The port number in the URL
     6. pathname - The path name of the URL
     7. search - The query portion of the URL
     8. hash - The anchor portion of the URL

124. How do get query string values in javascript

     You can use URLSearchParams to get query string values in javascript. Let's see an example to get the client code value from URL query string,

     var object = Object.create(null);

     02

125. How do you check if a key exists in an object

     You can check whether a key exists in an object or not using three approaches,

     1. Using in operator. You can use the in operator whether a key exists in an object or not

     var object = Object.create(null);

     03

     and If you want to check if a key doesn't exist, remember to use parenthesis,

     var object = Object.create(null);

     04
     1. Using hasOwnProperty method. You can use

        function func() {};
        
        new func(x, y, z);

        93 to particularly test for properties of the object instance (and not inherited properties)

     var object = Object.create(null);

     05
     1. Using undefined comparison. If you access a non-existing property from an object, the result is undefined. Let’s compare the properties against undefined to determine the existence of the property

     var object = Object.create(null);

     06

126. How do you loop through or enumerate javascript object

     You can use the

     function func() {};
     
     new func(x, y, z);

     94 loop to loop through javascript object. You can also make sure that the key you get is an actual property of an object, and doesn't come from the prototype using

     function func() {};
     
     new func(x, y, z);

     93 method

     var object = Object.create(null);

     07

127. How do you test for an empty object

     There are different solutions based on ECMAScript versions

     1. Using Object entries(ECMA 7+). You can use object entries length along with constructor type

     var object = Object.create(null);

     08
     1. Using Object keys(ECMA 5+). You can use object keys length along with constructor type

     var object = Object.create(null);

     09
     1. Using for-in with hasOwnProperty(Pre-ECMA 5). You can use a for-in loop along with hasOwnProperty

     var object = Object.create(null);

     10

128. What is an arguments object

     The arguments object is an Array-like object accessible inside functions that contains the values of the arguments passed to that function. For example, let's see how to use arguments object inside sum function,

     var object = Object.create(null);

     11

     Note. You can't apply array methods on arguments object. But you can convert into a regular array as below

     var object = Object.create(null);

     12

129. How do you make first letter of the string in an uppercase

     You can create a function which uses a chain of string methods such as charAt, toUpperCase and slice methods to generate a string with the first letter in uppercase

     var object = Object.create(null);

     13

130. What are the pros and cons of for loop

     The for-loop is a commonly used iteration syntax in javascript. It has both pros and cons

     Pros

     1. Works on every environment
     2. You can use break and continue flow control statements

     Cons

     1. Too verbose
     2. Imperative
     3. You might face one-by-off errors

131. How do you display the current date in javascript

     You can use

     function func() {};
     
     new func(x, y, z);

     96 to generate a new Date object containing the current date and time. For example, let's display the current date in mm/dd/yyyy

     var object = Object.create(null);

     14

132. How do you compare two date objects

     You need to use date. getTime() method to compare date values instead of comparison operators (==, . =, ===, and . == operators)

     var object = Object.create(null);

     15

133. How do you check if a string starts with another string

     You can use ECMAScript 6's

     function func() {};
     
     new func(x, y, z);

     97 method to check if a string starts with another string or not. But it is not yet supported in all browsers. Let's see an example to see this usage,

     var object = Object.create(null);

     16

134. How do you trim a string in javascript

     JavaScript provided a trim method on string types to trim any whitespaces present at the beginning or ending of the string

     var object = Object.create(null);

     17

     If your browser(

     var object = Object.create(null);

     18

135. How do you add a key value pair in javascript

     There are two possible solutions to add new properties to an object. Let's take a simple object to explain these solutions

     var object = Object.create(null);

     19
     1. Using dot notation. This solution is useful when you know the name of the property

     var object = Object.create(null);

     20
     1. Using square bracket notation. This solution is useful when the name of the property is dynamically determined

     var object = Object.create(null);

     21

136. Is the . -- notation represents a special operator

     No,that's not a special operator. Tapi itu adalah kombinasi dari 2 operator standar satu demi satu,

     1. A logical not (. )
     2. A prefix decrement (--)

     At first, the value decremented by one and then tested to see if it is equal to zero or not for determining the truthy/falsy value

137. Bagaimana Anda menetapkan nilai default ke variabel

     You can use the logical or operator

     function func() {};
     
     new func(x, y, z);

     98 in an assignment expression to provide a default value. The syntax looks like as below,

     var object = Object.create(null);

     22

     As per the above expression, variable 'a 'will get the value of 'c' only if 'b' is falsy (if is null, false, undefined, 0, empty string, or NaN), otherwise 'a' will get the value of 'b'

138. How do you define multiline strings

     You can define multiline string literals using the '\' character followed by line terminator

     var object = Object.create(null);

     23

     Tetapi jika Anda memiliki spasi setelah karakter '\', kode akan terlihat persis sama, tetapi akan memunculkan SyntaxError

139. Apa itu model shell aplikasi

     An application shell (or app shell) architecture is one way to build a Progressive Web App that reliably and instantly loads on your users' screens, similar to what you see in native applications. It is useful for getting some initial HTML to the screen fast without a network

140. Can we define properties for functions

     Yes, We can define properties for functions because functions are also objects

     var object = Object.create(null);

     24

141. What is the way to find the number of parameters expected by a function

     You can use

     function func() {};
     
     new func(x, y, z);

     99 syntax to find the number of parameters expected by a function. Let's take an example of

     // Create a new instance using function prototype.
     var newInstance = Object.create(func.prototype)
     
     // Call the function
     var result = func.call(newInstance, x, y, z),
     
     // If the result is a non-null object then use it otherwise just use the new instance.
     console.log(result && typeof result === 'object' ? result : newInstance);

     00 function to calculate the sum of numbers,

     var object = Object.create(null);

     25

142. What is a polyfill

     A polyfill is a piece of JS code used to provide modern functionality on older browsers that do not natively support it. For example, Silverlight plugin polyfill can be used to mimic the functionality of an HTML Canvas element on Microsoft Internet Explorer 7

143. What are break and continue statements

     The break statement is used to "jump out" of a loop. i. e, It breaks the loop and continues executing the code after the loop

     var object = Object.create(null);

     26

     The continue statement is used to "jump over" one iteration in the loop. i. e, It breaks one iteration (in the loop), if a specified condition occurs, and continues with the next iteration in the loop

     var object = Object.create(null);

     27

144. What are js labels

     The label statement allows us to name loops and blocks in JavaScript. We can then use these labels to refer back to the code later. For example, the below code with labels avoids printing the numbers when they are same,

     var object = Object.create(null);

     28

145. What are the benefits of keeping declarations at the top

     It is recommended to keep all declarations at the top of each script or function. The benefits of doing this are,

     1. Gives cleaner code
     2. It provides a single place to look for local variables
     3. Easy to avoid unwanted global variables
     4. It reduces the possibility of unwanted re-declarations

146. What are the benefits of initializing variables

     It is recommended to initialize variables because of the below benefits,

     1. It gives cleaner code
     2. It provides a single place to initialize variables
     3. Avoid undefined values in the code

147. What are the recommendations to create new object

     It is recommended to avoid creating new objects using

     // Create a new instance using function prototype.
     var newInstance = Object.create(func.prototype)
     
     // Call the function
     var result = func.call(newInstance, x, y, z),
     
     // If the result is a non-null object then use it otherwise just use the new instance.
     console.log(result && typeof result === 'object' ? result : newInstance);

     01. Instead you can initialize values based on it's type to create the objects
     1. Assign {} instead of new Object()
     2. Assign "" instead of new String()
     3. Assign 0 instead of new Number()
     4. Assign false instead of new Boolean()
     5. Assign [] instead of new Array()
     6. Assign /()/ instead of new RegExp()
     7. Assign function (){} instead of new Function()

     You can define them as an example,

     var object = Object.create(null);

     29

148. How do you define JSON arrays

     JSON arrays are written inside square brackets and arrays contain javascript objects. For example, the JSON array of users would be as below,

     var object = Object.create(null);

     30

149. How do you generate random integers

     You can use Math. random() with Math. floor() to return random integers. For example, if you want generate random integers between 1 to 10, the multiplication factor should be 10,

     var object = Object.create(null);

     31

     Note. Math. random() returns a random number between 0 (inclusive), and 1 (exclusive)

150. Can you write a random integers function to print integers with in a range

     Yes, you can create a proper random function to return a random number between min and max (both included)

     var object = Object.create(null);

     32

151. What is tree shaking

     Tree shaking is a form of dead code elimination. It means that unused modules will not be included in the bundle during the build process and for that it relies on the static structure of ES2015 module syntax,( i. e. import and export). Initially this has been popularized by the ES2015 module bundler

     // Create a new instance using function prototype.
     var newInstance = Object.create(func.prototype)
     
     // Call the function
     var result = func.call(newInstance, x, y, z),
     
     // If the result is a non-null object then use it otherwise just use the new instance.
     console.log(result && typeof result === 'object' ? result : newInstance);

     02

152. What is the need of tree shaking

     Tree Shaking can significantly reduce the code size in any application. i. e, The less code we send over the wire the more performant the application will be. For example, if we just want to create a “Hello World” Application using SPA frameworks then it will take around a few MBs, but by tree shaking it can bring down the size to just a few hundred KBs. Tree shaking is implemented in Rollup and Webpack bundlers

153. Is it recommended to use eval

     No, it allows arbitrary code to be run which causes a security problem. As we know that the eval() function is used to run text as code. In most of the cases, it should not be necessary to use it

154. What is a Regular Expression

     A regular expression is a sequence of characters that forms a search pattern. You can use this search pattern for searching data in a text. These can be used to perform all types of text search and text replace operations. Let's see the syntax format now,

     var object = Object.create(null);

     33

     For example, the regular expression or search pattern with case-insensitive username would be,

     var object = Object.create(null);

     34

155. What are the string methods available in Regular expression

     Regular Expressions has two string methods. search() and replace(). The search() method uses an expression to search for a match, and returns the position of the match

     var object = Object.create(null);

     35

     The replace() method is used to return a modified string where the pattern is replaced

     var object = Object.create(null);

     36

156. What are modifiers in regular expression

     Modifiers can be used to perform case-insensitive and global searches. Let's list down some of the modifiers,

     ModifierDescriptioniPerform case-insensitive matchinggPerform a global match rather than stops at first matchmPerform multiline matching

     Let's take an example of global modifier,

     var object = Object.create(null);

     37

157. What are regular expression patterns

     Regular Expressions provide a group of patterns in order to match characters. Pada dasarnya mereka dikategorikan menjadi 3 jenis,

     1. Brackets. These are used to find a range of characters. For example, below are some use cases,
        1. [abc]. Used to find any of the characters between the brackets(a,b,c)
        2. [0-9]. Used to find any of the digits between the brackets
        3. (A. B). Digunakan untuk menemukan salah satu alternatif yang dipisahkan dengan
     2. Metacharacters. These are characters with a special meaning For example, below are some use cases,
        1. \d. Used to find a digit
        2. \s. Used to find a whitespace character
        3. \b. Used to find a match at the beginning or ending of a word
     3. Quantifiers. These are useful to define quantities For example, below are some use cases,
        1. n+. Used to find matches for any string that contains at least one n
        2. n*. Used to find matches for any string that contains zero or more occurrences of n
        3. n?. Used to find matches for any string that contains zero or one occurrences of n

158. What is a RegExp object

     RegExp object is a regular expression object with predefined properties and methods. Let's see the simple usage of RegExp object,

     var object = Object.create(null);

     38

159. How do you search a string for a pattern

     You can use the test() method of regular expression in order to search a string for a pattern, and return true or false depending on the result

     var object = Object.create(null);

     39

160. What is the purpose of exec method

     The purpose of exec method is similar to test method but it executes a search for a match in a specified string and returns a result array, or null instead of returning true/false

     var object = Object.create(null);

     40

161. How do you change the style of a HTML element

     You can change inline style or classname of a HTML element using javascript

     1. Using style property. You can modify inline style using style property

     var object = Object.create(null);

     41
     1. Using ClassName property. It is easy to modify element class using className property

     var object = Object.create(null);

     42

162. What would be the result of 1+2+'3'

     The output is going to be

     // Create a new instance using function prototype.
     var newInstance = Object.create(func.prototype)
     
     // Call the function
     var result = func.call(newInstance, x, y, z),
     
     // If the result is a non-null object then use it otherwise just use the new instance.
     console.log(result && typeof result === 'object' ? result : newInstance);

     03. Since

     // Create a new instance using function prototype.
     var newInstance = Object.create(func.prototype)
     
     // Call the function
     var result = func.call(newInstance, x, y, z),
     
     // If the result is a non-null object then use it otherwise just use the new instance.
     console.log(result && typeof result === 'object' ? result : newInstance);

     04 and

     // Create a new instance using function prototype.
     var newInstance = Object.create(func.prototype)
     
     // Call the function
     var result = func.call(newInstance, x, y, z),
     
     // If the result is a non-null object then use it otherwise just use the new instance.
     console.log(result && typeof result === 'object' ? result : newInstance);

     05 are numeric values, the result of the first two digits is going to be a numeric value

     // Create a new instance using function prototype.
     var newInstance = Object.create(func.prototype)
     
     // Call the function
     var result = func.call(newInstance, x, y, z),
     
     // If the result is a non-null object then use it otherwise just use the new instance.
     console.log(result && typeof result === 'object' ? result : newInstance);

     06. The next digit is a string type value because of that the addition of numeric value

     // Create a new instance using function prototype.
     var newInstance = Object.create(func.prototype)
     
     // Call the function
     var result = func.call(newInstance, x, y, z),
     
     // If the result is a non-null object then use it otherwise just use the new instance.
     console.log(result && typeof result === 'object' ? result : newInstance);

     06 and string type value

     // Create a new instance using function prototype.
     var newInstance = Object.create(func.prototype)
     
     // Call the function
     var result = func.call(newInstance, x, y, z),
     
     // If the result is a non-null object then use it otherwise just use the new instance.
     console.log(result && typeof result === 'object' ? result : newInstance);

     06 is just going to be a concatenation value

     // Create a new instance using function prototype.
     var newInstance = Object.create(func.prototype)
     
     // Call the function
     var result = func.call(newInstance, x, y, z),
     
     // If the result is a non-null object then use it otherwise just use the new instance.
     console.log(result && typeof result === 'object' ? result : newInstance);

     03

163. What is a debugger statement

     The debugger statement invokes any available debugging functionality, such as setting a breakpoint. If no debugging functionality is available, this statement has no effect. For example, in the below function a debugger statement has been inserted. So execution is paused at the debugger statement just like a breakpoint in the script source

     var object = Object.create(null);

     43

164. What is the purpose of breakpoints in debugging

     You can set breakpoints in the javascript code once the debugger statement is executed and the debugger window pops up. At each breakpoint, javascript will stop executing, and let you examine the JavaScript values. After examining values, you can resume the execution of code using the play button

165. Can I use reserved words as identifiers

     No, you cannot use the reserved words as variables, labels, object or function names. Let's see one simple example,

     var object = Object.create(null);

     44

166. How do you detect a mobile browser

     You can use regex which returns a true or false value depending on whether or not the user is browsing with a mobile

     var object = Object.create(null);

     45

167. How do you detect a mobile browser without regexp

     You can detect mobile browsers by simply running through a list of devices and checking if the useragent matches anything. This is an alternative solution for RegExp usage,

     var object = Object.create(null);

     46

168. How do you get the image width and height using JS

     You can programmatically get the image and check the dimensions(width and height) using Javascript

     var object = Object.create(null);

     47

169. How do you make synchronous HTTP request

     Browser menyediakan objek XMLHttpRequest yang dapat digunakan untuk membuat permintaan HTTP sinkron dari JavaScript

     var object = Object.create(null);

     48

170. How do you make asynchronous HTTP request

     Browsers provide an XMLHttpRequest object which can be used to make asynchronous HTTP requests from JavaScript by passing the 3rd parameter as true

     var object = Object.create(null);

     49

171. How do you convert date to another timezone in javascript

     You can use the toLocaleString() method to convert dates in one timezone to another. For example, let's convert current date to British English timezone as below,

     var object = Object.create(null);

     50

172. What are the properties used to get size of window

     You can use innerWidth, innerHeight, clientWidth, clientHeight properties of windows, document element and document body objects to find the size of a window. Let's use them combination of these properties to calculate the size of a window or document,

     var object = Object.create(null);

     51

173. What is a conditional operator in javascript

     The conditional (ternary) operator is the only JavaScript operator that takes three operands which acts as a shortcut for if statements

     var object = Object.create(null);

     52

174. Can you apply chaining on conditional operator

     Yes, you can apply chaining on conditional operators similar to if … else if … else if … else chain. The syntax is going to be as below,

     var object = Object.create(null);

     53

175. What are the ways to execute javascript after page load

     You can execute javascript after page load in many different ways,

     1. window. onload

     var object = Object.create(null);

     54
     1. document. onload

     var object = Object.create(null);

     55
     1. beban tubuh

     var object = Object.create(null);

     56

176. What is the difference between proto and prototype

     The

     // Create a new instance using function prototype.
     var newInstance = Object.create(func.prototype)
     
     // Call the function
     var result = func.call(newInstance, x, y, z),
     
     // If the result is a non-null object then use it otherwise just use the new instance.
     console.log(result && typeof result === 'object' ? result : newInstance);

     10 object is the actual object that is used in the lookup chain to resolve methods, etc. Whereas

     // Create a new instance using function prototype.
     var newInstance = Object.create(func.prototype)
     
     // Call the function
     var result = func.call(newInstance, x, y, z),
     
     // If the result is a non-null object then use it otherwise just use the new instance.
     console.log(result && typeof result === 'object' ? result : newInstance);

     11 is the object that is used to build

     // Create a new instance using function prototype.
     var newInstance = Object.create(func.prototype)
     
     // Call the function
     var result = func.call(newInstance, x, y, z),
     
     // If the result is a non-null object then use it otherwise just use the new instance.
     console.log(result && typeof result === 'object' ? result : newInstance);

     10 when you create an object with new

     var object = Object.create(null);

     _57

     There are few more differences,

     featurePrototypeprotoAccessAll the function constructors have prototype properties. All the objects have __proto__ propertyPurposeUsed to reduce memory wastage with a single copy of functionUsed in lookup chain to resolve methods, constructors etc. ECMAScriptIntroduced in ES6Introduced in ES5UsageFrequently usedRarely used

177. Give an example where do you really need semicolon

     It is recommended to use semicolons after every statement in JavaScript. For example, in the below case it throws an error ". is not a function" at runtime due to missing semicolon

     var object = Object.create(null);

     _58

     and it will be interpreted as

     var object = Object.create(null);

     59

     In this case, we are passing the second function as an argument to the first function and then trying to call the result of the first function call as a function. Hence, the second function will fail with a ". is not a function" error at runtime

178. What is a freeze method

     The freeze() method is used to freeze an object. Freezing an object does not allow adding new properties to an object,prevents from removing and prevents changing the enumerability, configurability, or writability of existing properties. i. e, It returns the passed object and does not create a frozen copy

     var object = Object.create(null);

     60

     Remember freezing is only applied to the top-level properties in objects but not for nested objects. For example, let's try to freeze user object which has employment details as nested object and observe that details have been changed

     var object = Object.create(null);

     61

     Catatan. It causes a TypeError if the argument passed is not an object

179. What is the purpose of freeze method

     Below are the main benefits of using freeze method,

     1. It is used for freezing objects and arrays
     2. It is used to make an object immutable

180. Why do I need to use freeze method

     In the Object-oriented paradigm, an existing API contains certain elements that are not intended to be extended, modified, or re-used outside of their current context. Hence it works as the

     // Create a new instance using function prototype.
     var newInstance = Object.create(func.prototype)
     
     // Call the function
     var result = func.call(newInstance, x, y, z),
     
     // If the result is a non-null object then use it otherwise just use the new instance.
     console.log(result && typeof result === 'object' ? result : newInstance);

     13 keyword which is used in various languages

181. How do you detect a browser language preference

     You can use navigator object to detect a browser language preference as below,

     var object = Object.create(null);

     62

182. How to convert string to title case with javascript

     Title case means that the first letter of each word is capitalized. You can convert a string to title case using the below function,

     var object = Object.create(null);

     63

183. How do you detect javascript disabled in the page

     You can use the

     // Create a new instance using function prototype.
     var newInstance = Object.create(func.prototype)
     
     // Call the function
     var result = func.call(newInstance, x, y, z),
     
     // If the result is a non-null object then use it otherwise just use the new instance.
     console.log(result && typeof result === 'object' ? result : newInstance);

     14 tag to detect javascript disabled or not. The code block inside

     // Create a new instance using function prototype.
     var newInstance = Object.create(func.prototype)
     
     // Call the function
     var result = func.call(newInstance, x, y, z),
     
     // If the result is a non-null object then use it otherwise just use the new instance.
     console.log(result && typeof result === 'object' ? result : newInstance);

     14 gets executed when JavaScript is disabled, and is typically used to display alternative content when the page generated in JavaScript

     var object = Object.create(null);

     64

184. What are various operators supported by javascript

     An operator is capable of manipulating(mathematical and logical computations) a certain value or operand. There are various operators supported by JavaScript as below,

     1. Arithmetic Operators. Includes + (Addition),– (Subtraction), * (Multiplication), / (Division), % (Modulus), + + (Increment) and – – (Decrement)
     2. Comparison Operators. Includes = =(Equal),. = (Not Equal), ===(Equal with type), > (Greater than),> = (Greater than or Equal to),< (Less than),<= (Less than or Equal to)
     3. Logical Operators. Includes &&(Logical AND),. (Logical OR),. (Logical NOT)
     4. Assignment Operators. Includes = (Assignment Operator), += (Add and Assignment Operator), – = (Subtract and Assignment Operator), *= (Multiply and Assignment), /= (Divide and Assignment), %= (Modules and Assignment)
     5. Ternary Operators. It includes conditional(. ?) Operator
     6. typeof Operator. It uses to find type of variable. The syntax looks like

        // Create a new instance using function prototype.
        var newInstance = Object.create(func.prototype)
        
        // Call the function
        var result = func.call(newInstance, x, y, z),
        
        // If the result is a non-null object then use it otherwise just use the new instance.
        console.log(result && typeof result === 'object' ? result : newInstance);

        16

185. What is a rest parameter

     Rest parameter is an improved way to handle function parameters which allows us to represent an indefinite number of arguments as an array. The syntax would be as below,

     var object = Object.create(null);

     65

     For example, let's take a sum example to calculate on dynamic number of parameters,

     var object = Object.create(null);

     66

     Note. Rest parameter is added in ES2015 or ES6

186. What happens if you do not use rest parameter as a last argument

     The rest parameter should be the last argument, as its job is to collect all the remaining arguments into an array. For example, if you define a function like below it doesn’t make any sense and will throw an error

     var object = Object.create(null);

     67

187. What are the bitwise operators available in javascript

     Below are the list of bitwise logical operators used in JavaScript

     1. Bitwise AND ( & )
     2. Searah bit ATAU (. )
     3. Bitwise XOR ( ^ )
     4. Bitwise NOT ( ~ )
     5. Pergeseran Kiri ( << )
     6. Sign Propagating Right Shift ( >> )
     7. Zero fill Right Shift ( >>> )

188. What is a spread operator

     Spread operator allows iterables( arrays / objects / strings ) to be expanded into single arguments/elements. Let's take an example to see this behavior,

     var object = Object.create(null);

     68

189. How do you determine whether object is frozen or not

     Object. isFrozen() method is used to determine if an object is frozen or not. An object is frozen if all of the below conditions hold true,

     1. If it is not extensible
     2. If all of its properties are non-configurable
     3. If all its data properties are non-writable. The usage is going to be as follows,

     var object = Object.create(null);

     69

190. How do you determine two values same or not using object

     The Object. is() method determines whether two values are the same value. For example, the usage with different types of values would be,

     var object = Object.create(null);

     70

     Two values are the same if one of the following holds

     1. both undefined
     2. both null
     3. both true or both false
     4. both strings of the same length with the same characters in the same order
     5. both the same object (means both object have same reference)
     6. both numbers and both +0 both -0 both NaN both non-zero and both not NaN and both have the same value

191. What is the purpose of using object is method

     Some of the applications of Object's

     // Create a new instance using function prototype.
     var newInstance = Object.create(func.prototype)
     
     // Call the function
     var result = func.call(newInstance, x, y, z),
     
     // If the result is a non-null object then use it otherwise just use the new instance.
     console.log(result && typeof result === 'object' ? result : newInstance);

     17 method are follows,
     1. It is used for comparison of two strings
     2. Ini digunakan untuk perbandingan dua angka
     3. Ini digunakan untuk membandingkan polaritas dua angka
     4. It is used for comparison of two objects

192. How do you copy properties from one object to other

     You can use the Object. assign() method which is used to copy the values and properties from one or more source objects to a target object. It returns the target object which has properties and values copied from the source objects. The syntax would be as below,

     var object = Object.create(null);

     71

     Let's take example with one source and one target object,

     var object = Object.create(null);

     72

     As observed in the above code, there is a common property(

     // Create a new instance using function prototype.
     var newInstance = Object.create(func.prototype)
     
     // Call the function
     var result = func.call(newInstance, x, y, z),
     
     // If the result is a non-null object then use it otherwise just use the new instance.
     console.log(result && typeof result === 'object' ? result : newInstance);

     18) from source to target so it's value has been overwritten

193. What are the applications of assign method

     Below are the some of main applications of Object. assign() method,

     1. It is used for cloning an object
     2. It is used to merge objects with the same properties

194. What is a proxy object

     The Proxy object is used to define custom behavior for fundamental operations such as property lookup, assignment, enumeration, function invocation, etc. The syntax would be as follows,

     var object = Object.create(null);

     73

     Mari kita ambil contoh objek proxy,

     var object = Object.create(null);

     74

     In the above code, it uses

     // Create a new instance using function prototype.
     var newInstance = Object.create(func.prototype)
     
     // Call the function
     var result = func.call(newInstance, x, y, z),
     
     // If the result is a non-null object then use it otherwise just use the new instance.
     console.log(result && typeof result === 'object' ? result : newInstance);

     19 handler which define the behavior of the proxy when an operation is performed on it

195. What is the purpose of seal method

     The Object. seal() method is used to seal an object, by preventing new properties from being added to it and marking all existing properties as non-configurable. But values of present properties can still be changed as long as they are writable. Let's see the below example to understand more about seal() method

     var object = Object.create(null);

     75

196. What are the applications of seal method

     Below are the main applications of Object. seal() method,

     1. It is used for sealing objects and arrays
     2. It is used to make an object immutable

197. What are the differences between freeze and seal methods

     If an object is frozen using the Object. freeze() method then its properties become immutable and no changes can be made in them whereas if an object is sealed using the Object. seal() method then the changes can be made in the existing properties of the object

198. How do you determine if an object is sealed or not

     The Object. isSealed() method is used to determine if an object is sealed or not. An object is sealed if all of the below conditions hold true

     1. If it is not extensible
     2. If all of its properties are non-configurable
     3. If it is not removable (but not necessarily non-writable). Let's see it in the action

     var object = Object.create(null);

     76

199. How do you get enumerable key and value pairs

     The Object. entries() method is used to return an array of a given object's own enumerable string-keyed property [key, value] pairs, in the same order as that provided by a for. in loop. Let's see the functionality of object. entries() method in an example,

     var object = Object.create(null);

     77

     Note. The order is not guaranteed as object defined

200. What is the main difference between Object. values and Object. entries method

     The Object. values() method's behavior is similar to Object. entries() method but it returns an array of values instead [key,value] pairs

     var object = Object.create(null);

     78

201. How can you get the list of keys of any object

     You can use the

     // Create a new instance using function prototype.
     var newInstance = Object.create(func.prototype)
     
     // Call the function
     var result = func.call(newInstance, x, y, z),
     
     // If the result is a non-null object then use it otherwise just use the new instance.
     console.log(result && typeof result === 'object' ? result : newInstance);

     20 method which is used to return an array of a given object's own property names, in the same order as we get with a normal loop. For example, you can get the keys of a user object,

     var object = Object.create(null);

     79

202. How do you create an object with prototype

     The Object. create() method is used to create a new object with the specified prototype object and properties. i. e, It uses an existing object as the prototype of the newly created object. It returns a new object with the specified prototype object and properties

     var object = Object.create(null);

     80

203. What is a WeakSet

     WeakSet is used to store a collection of weakly(weak references) held objects. The syntax would be as follows,

     var object = Object.create(null);

     81

     Let's see the below example to explain it's behavior,

     var object = Object.create(null);

     _82

204. What are the differences between WeakSet and Set

     The main difference is that references to objects in Set are strong while references to objects in WeakSet are weak. i. e, An object in WeakSet can be garbage collected if there is no other reference to it. Other differences are,

     1. Sets can store any value Whereas WeakSets can store only collections of objects
     2. WeakSet does not have size property unlike Set
     3. WeakSet does not have methods such as clear, keys, values, entries, forEach
     4. WeakSet is not iterable

205. List down the collection of methods available on WeakSet

     Below are the list of methods available on WeakSet,

     1. add(value). A new object is appended with the given value to the weakset
     2. delete(value). Deletes the value from the WeakSet collection
     3. has(value). It returns true if the value is present in the WeakSet Collection, otherwise it returns false

     Let's see the functionality of all the above methods in an example,

     var object = Object.create(null);

     83

206. What is a WeakMap

     The WeakMap object is a collection of key/value pairs in which the keys are weakly referenced. In this case, keys must be objects and the values can be arbitrary values. The syntax is looking like as below,

     var object = Object.create(null);

     84

     Let's see the below example to explain it's behavior,

     var object = Object.create(null);

     85

207. What are the differences between WeakMap and Map

     The main difference is that references to key objects in Map are strong while references to key objects in WeakMap are weak. i. e, A key object in WeakMap can be garbage collected if there is no other reference to it. Other differences are,

     1. Maps can store any key type Whereas WeakMaps can store only collections of key objects
     2. WeakMap does not have size property unlike Map
     3. WeakMap does not have methods such as clear, keys, values, entries, forEach
     4. WeakMap is not iterable

208. Buat daftar kumpulan metode yang tersedia di WeakMap

     Below are the list of methods available on WeakMap,

     1. set(key, value). Sets the value for the key in the WeakMap object. Returns the WeakMap object
     2. delete(key). Menghapus nilai apa pun yang terkait dengan kunci
     3. memiliki (kunci). Mengembalikan pernyataan Boolean apakah suatu nilai telah dikaitkan dengan kunci di objek WeakMap atau tidak
     4. dapatkan (kunci). Mengembalikan nilai yang terkait dengan kunci, atau tidak terdefinisi jika tidak ada. Mari kita lihat fungsionalitas dari semua metode di atas dalam sebuah contoh,

     var object = Object.create(null);

     _86

209. Apa tujuan dari ketidaksetaraan

     uneval() adalah fungsi bawaan yang digunakan untuk membuat representasi string dari kode sumber suatu Objek. Ini adalah fungsi tingkat atas dan tidak terkait dengan objek apa pun. Mari kita lihat contoh di bawah ini untuk mengetahui lebih banyak tentang fungsinya,

     var object = Object.create(null);

     _87

210. Bagaimana Anda menyandikan URL

     Fungsi encodeURI() digunakan untuk menyandikan URI lengkap yang memiliki karakter khusus kecuali (, / ?. @ & = + $ #) karakter

     var object = Object.create(null);

     _88

211. Bagaimana Anda memecahkan kode URL

     The decodeURI() function is used to decode a Uniform Resource Identifier (URI) previously created by encodeURI()

     var object = Object.create(null);

     89

212. How do you print the contents of web page

     The window object provided a print() method which is used to print the contents of the current window. It opens a Print dialog box which lets you choose between various printing options. Let's see the usage of print method in an example,

     var object = Object.create(null);

     90

     Note. In most browsers, it will block while the print dialog is open

213. What is the difference between uneval and eval

     The

     // Create a new instance using function prototype.
     var newInstance = Object.create(func.prototype)
     
     // Call the function
     var result = func.call(newInstance, x, y, z),
     
     // If the result is a non-null object then use it otherwise just use the new instance.
     console.log(result && typeof result === 'object' ? result : newInstance);

     21 function returns the source of a given object; whereas the

     // Create a new instance using function prototype.
     var newInstance = Object.create(func.prototype)
     
     // Call the function
     var result = func.call(newInstance, x, y, z),
     
     // If the result is a non-null object then use it otherwise just use the new instance.
     console.log(result && typeof result === 'object' ? result : newInstance);

     22 function does the opposite, by evaluating that source code in a different memory area. Let's see an example to clarify the difference,

     var object = Object.create(null);

     91

214. What is an anonymous function

     An anonymous function is a function without a name. Anonymous functions are commonly assigned to a variable name or used as a callback function. The syntax would be as below,

     var object = Object.create(null);

     92

     Let's see the above anonymous function in an example,

     var object = Object.create(null);

     93

215. What is the precedence order between local and global variables

     A local variable takes precedence over a global variable with the same name. Let's see this behavior in an example

     var object = Object.create(null);

     _94

216. What are javascript accessors

     ECMAScript 5 introduced javascript object accessors or computed properties through getters and setters. Getters uses the

     // Create a new instance using function prototype.
     var newInstance = Object.create(func.prototype)
     
     // Call the function
     var result = func.call(newInstance, x, y, z),
     
     // If the result is a non-null object then use it otherwise just use the new instance.
     console.log(result && typeof result === 'object' ? result : newInstance);

     19 keyword whereas Setters uses the

     // Create a new instance using function prototype.
     var newInstance = Object.create(func.prototype)
     
     // Call the function
     var result = func.call(newInstance, x, y, z),
     
     // If the result is a non-null object then use it otherwise just use the new instance.
     console.log(result && typeof result === 'object' ? result : newInstance);

     24 keyword

     var object = Object.create(null);

     95

217. How do you define property on Object constructor

     The Object. defineProperty() static method is used to define a new property directly on an object, or modify an existing property on an object, and returns the object. Let's see an example to know how to define property,

     var object = Object.create(null);

     96

218. What is the difference between get and defineProperty

     Both have similar results until unless you use classes. If you use

     // Create a new instance using function prototype.
     var newInstance = Object.create(func.prototype)
     
     // Call the function
     var result = func.call(newInstance, x, y, z),
     
     // If the result is a non-null object then use it otherwise just use the new instance.
     console.log(result && typeof result === 'object' ? result : newInstance);

     19 the property will be defined on the prototype of the object whereas using

     // Create a new instance using function prototype.
     var newInstance = Object.create(func.prototype)
     
     // Call the function
     var result = func.call(newInstance, x, y, z),
     
     // If the result is a non-null object then use it otherwise just use the new instance.
     console.log(result && typeof result === 'object' ? result : newInstance);

     26 the property will be defined on the instance it is applied to

219. What are the advantages of Getters and Setters

     Below are the list of benefits of Getters and Setters,

     1. They provide simpler syntax
     2. They are used for defining computed properties, or accessors in JS
     3. Useful to provide equivalence relation between properties and methods
     4. They can provide better data quality
     5. Useful for doing things behind the scenes with the encapsulated logic

220. Can I add getters and setters using defineProperty method

     Yes, You can use the

     // Create a new instance using function prototype.
     var newInstance = Object.create(func.prototype)
     
     // Call the function
     var result = func.call(newInstance, x, y, z),
     
     // If the result is a non-null object then use it otherwise just use the new instance.
     console.log(result && typeof result === 'object' ? result : newInstance);

     26 method to add Getters and Setters. For example, the below counter object uses increment, decrement, add and subtract properties,

     var object = Object.create(null);

     97

221. What is the purpose of switch-case

     The switch case statement in JavaScript is used for decision making purposes. In a few cases, using the switch case statement is going to be more convenient than if-else statements. The syntax would be as below,

     var object = Object.create(null);

     98

     The above multi-way branch statement provides an easy way to dispatch execution to different parts of code based on the value of the expression

222. What are the conventions to be followed for the usage of switch case

     Below are the list of conventions should be taken care,

     1. The expression can be of type either number or string
     2. Duplicate values are not allowed for the expression
     3. The default statement is optional. If the expression passed to switch does not match with any case value then the statement within default case will be executed
     4. The break statement is used inside the switch to terminate a statement sequence
     5. The break statement is optional. But if it is omitted, the execution will continue on into the next case

223. What are primitive data types

     A primitive data type is data that has a primitive value (which has no properties or methods). There are 7 types of primitive data types

     1. string
     2. number
     3. boolean
     4. null
     5. undefined
     6. bigint
     7. symbol

224. What are the different ways to access object properties

     There are 3 possible ways for accessing the property of an object

     1. Dot notation. It uses dot for accessing the properties

     var object = Object.create(null);

     99
     1. Square brackets notation. It uses square brackets for property access

     var object = {
          name: "Sudheer",
          age: 34
     };
     
     Object literal property values can be of any data type, including array, function, and nested object.

     00
     1. Expression notation. Ini menggunakan ekspresi dalam tanda kurung siku

     var object = {
          name: "Sudheer",
          age: 34
     };
     
     Object literal property values can be of any data type, including array, function, and nested object.

     01

225. What are the function parameter rules

     JavaScript functions follow below rules for parameters,

     1. The function definitions do not specify data types for parameters
     2. Jangan melakukan pengecekan tipe pada argumen yang diteruskan
     3. Do not check the number of arguments received. i. e, The below function follows the above rules,

     var object = {
          name: "Sudheer",
          age: 34
     };
     
     Object literal property values can be of any data type, including array, function, and nested object.

     02

226. What is an error object

     Objek kesalahan adalah objek kesalahan bawaan yang menyediakan informasi kesalahan saat terjadi kesalahan. It has two properties. name and message. For example, the below function logs error details,

     var object = {
          name: "Sudheer",
          age: 34
     };
     
     Object literal property values can be of any data type, including array, function, and nested object.

     03

227. When you get a syntax error

     A SyntaxError is thrown if you try to evaluate code with a syntax error. For example, the below missing quote for the function parameter throws a syntax error

     var object = {
          name: "Sudheer",
          age: 34
     };
     
     Object literal property values can be of any data type, including array, function, and nested object.

     04

228. What are the different error names from error object

     There are 6 different types of error names returned from error object,

     Error NameDescriptionEvalErrorAn error has occurred in the eval() functionRangeErrorAn error has occurred with a number "out of range"ReferenceErrorAn error due to an illegal referenceSyntaxErrorAn error due to a syntax errorTypeErrorAn error due to a type errorURIErrorAn error due to encodeURI()

229. What are the various statements in error handling

     Below are the list of statements used in an error handling,

     1. try. This statement is used to test a block of code for errors
     2. catch. This statement is used to handle the error
     3. throw. This statement is used to create custom errors
     4. finally. This statement is used to execute code after try and catch regardless of the result

230. What are the two types of loops in javascript

     1. Entry Controlled loops. In this kind of loop type, the test condition is tested before entering the loop body. For example, For Loop and While Loop comes under this category
     2. Exit Controlled Loops. In this kind of loop type, the test condition is tested or evaluated at the end of the loop body. i. e, the loop body will execute at least once irrespective of test condition true or false. For example, do-while loop comes under this category

231. What is nodejs

     Node. js is a server-side platform built on Chrome's JavaScript runtime for easily building fast and scalable network applications. It is an event-based, non-blocking, asynchronous I/O runtime that uses Google's V8 JavaScript engine and libuv library

232. What is an Intl object

     The Intl object is the namespace for the ECMAScript Internationalization API, which provides language sensitive string comparison, number formatting, and date and time formatting. It provides access to several constructors and language sensitive functions

233. How do you perform language specific date and time formatting

     You can use the

     // Create a new instance using function prototype.
     var newInstance = Object.create(func.prototype)
     
     // Call the function
     var result = func.call(newInstance, x, y, z),
     
     // If the result is a non-null object then use it otherwise just use the new instance.
     console.log(result && typeof result === 'object' ? result : newInstance);

     28 object which is a constructor for objects that enable language-sensitive date and time formatting. Let's see this behavior with an example,

     var object = {
          name: "Sudheer",
          age: 34
     };
     
     Object literal property values can be of any data type, including array, function, and nested object.

     05

234. What is an Iterator

     An iterator is an object which defines a sequence and a return value upon its termination. It implements the Iterator protocol with a

     // Create a new instance using function prototype.
     var newInstance = Object.create(func.prototype)
     
     // Call the function
     var result = func.call(newInstance, x, y, z),
     
     // If the result is a non-null object then use it otherwise just use the new instance.
     console.log(result && typeof result === 'object' ? result : newInstance);

     29 method which returns an object with two properties.

     // Create a new instance using function prototype.
     var newInstance = Object.create(func.prototype)
     
     // Call the function
     var result = func.call(newInstance, x, y, z),
     
     // If the result is a non-null object then use it otherwise just use the new instance.
     console.log(result && typeof result === 'object' ? result : newInstance);

     30 (the next value in the sequence) and

     // Create a new instance using function prototype.
     var newInstance = Object.create(func.prototype)
     
     // Call the function
     var result = func.call(newInstance, x, y, z),
     
     // If the result is a non-null object then use it otherwise just use the new instance.
     console.log(result && typeof result === 'object' ? result : newInstance);

     31 (which is true if the last value in the sequence has been consumed)

235. How does synchronous iteration works

     Synchronous iteration was introduced in ES6 and it works with below set of components,

     Iterable. It is an object which can be iterated over via a method whose key is Symbol. iterator. Iterator. It is an object returned by invoking

     // Create a new instance using function prototype.
     var newInstance = Object.create(func.prototype)
     
     // Call the function
     var result = func.call(newInstance, x, y, z),
     
     // If the result is a non-null object then use it otherwise just use the new instance.
     console.log(result && typeof result === 'object' ? result : newInstance);

     32 on an iterable. This iterator object wraps each iterated element in an object and returns it via

     // Create a new instance using function prototype.
     var newInstance = Object.create(func.prototype)
     
     // Call the function
     var result = func.call(newInstance, x, y, z),
     
     // If the result is a non-null object then use it otherwise just use the new instance.
     console.log(result && typeof result === 'object' ? result : newInstance);

     29 method one by one. IteratorResult. It is an object returned by

     // Create a new instance using function prototype.
     var newInstance = Object.create(func.prototype)
     
     // Call the function
     var result = func.call(newInstance, x, y, z),
     
     // If the result is a non-null object then use it otherwise just use the new instance.
     console.log(result && typeof result === 'object' ? result : newInstance);

     29 method. The object contains two properties; the

     // Create a new instance using function prototype.
     var newInstance = Object.create(func.prototype)
     
     // Call the function
     var result = func.call(newInstance, x, y, z),
     
     // If the result is a non-null object then use it otherwise just use the new instance.
     console.log(result && typeof result === 'object' ? result : newInstance);

     30 property contains an iterated element and the

     // Create a new instance using function prototype.
     var newInstance = Object.create(func.prototype)
     
     // Call the function
     var result = func.call(newInstance, x, y, z),
     
     // If the result is a non-null object then use it otherwise just use the new instance.
     console.log(result && typeof result === 'object' ? result : newInstance);

     31 property determines whether the element is the last element or not

     Let's demonstrate synchronous iteration with an array as below,

     var object = {
          name: "Sudheer",
          age: 34
     };
     
     Object literal property values can be of any data type, including array, function, and nested object.

     06

236. What is an event loop

     The Event Loop is a queue of callback functions. When an async function executes, the callback function is pushed into the queue. The JavaScript engine doesn't start processing the event loop until the async function has finished executing the code. Note. It allows Node. js to perform non-blocking I/O operations even though JavaScript is single-threaded

237. What is call stack

     Call Stack is a data structure for javascript interpreters to keep track of function calls(creates execution context) in the program. It has two major actions,

     1. Whenever you call a function for its execution, you are pushing it to the stack
     2. Whenever the execution is completed, the function is popped out of the stack

     Let's take an example and it's state representation in a diagram format

     var object = {
          name: "Sudheer",
          age: 34
     };
     
     Object literal property values can be of any data type, including array, function, and nested object.

     07

     The above code processed in a call stack as below,

     1. Add the

        // Create a new instance using function prototype.
        var newInstance = Object.create(func.prototype)
        
        // Call the function
        var result = func.call(newInstance, x, y, z),
        
        // If the result is a non-null object then use it otherwise just use the new instance.
        console.log(result && typeof result === 'object' ? result : newInstance);

        37 function to the call stack list and execute the code
     2. Add the

        // Create a new instance using function prototype.
        var newInstance = Object.create(func.prototype)
        
        // Call the function
        var result = func.call(newInstance, x, y, z),
        
        // If the result is a non-null object then use it otherwise just use the new instance.
        console.log(result && typeof result === 'object' ? result : newInstance);

        38 function to the call stack list and execute the code
     3. Delete the

        // Create a new instance using function prototype.
        var newInstance = Object.create(func.prototype)
        
        // Call the function
        var result = func.call(newInstance, x, y, z),
        
        // If the result is a non-null object then use it otherwise just use the new instance.
        console.log(result && typeof result === 'object' ? result : newInstance);

        38 function from our call stack list
     4. Delete the

        // Create a new instance using function prototype.
        var newInstance = Object.create(func.prototype)
        
        // Call the function
        var result = func.call(newInstance, x, y, z),
        
        // If the result is a non-null object then use it otherwise just use the new instance.
        console.log(result && typeof result === 'object' ? result : newInstance);

        37 function from the call stack list since there are no items anymore
     

238. What is an event queue

     The event queue follows the queue data structure. It stores async callbacks to be added to the call stack. It is also known as the Callback Queue or Macrotask Queue

     Whenever the call stack receives an async function, it is moved into the Web API. Based on the function, Web API executes it and awaits the result. Once it is finished, it moves the callback into the event queue (the callback of the promise is moved into the microtask queue)

     The event queue constantly checks whether or not the call stack is empty. Once the call stack is empty and there is a callback in the event queue, the event queue moves the callback into the call stack. If there is a callback in the microtask queue as well, it is moved first. The microtask queue has a higher priority than the event queue

239. What is a decorator

     A decorator is an expression that evaluates to a function and that takes the target, name, and decorator descriptor as arguments. Also, it optionally returns a decorator descriptor to install on the target object. Let's define admin decorator for user class at design time,

     var object = {
          name: "Sudheer",
          age: 34
     };
     
     Object literal property values can be of any data type, including array, function, and nested object.

     08

240. What are the properties of Intl object

     Below are the list of properties available on Intl object,

     1. Collator. These are the objects that enable language-sensitive string comparison
     2. DateTimeFormat. These are the objects that enable language-sensitive date and time formatting
     3. ListFormat. These are the objects that enable language-sensitive list formatting
     4. NumberFormat. Objects that enable language-sensitive number formatting
     5. PluralRules. Objects that enable plural-sensitive formatting and language-specific rules for plurals
     6. Format Waktu Relatif. Objects that enable language-sensitive relative time formatting

241. What is an Unary operator

     The unary(+) operator is used to convert a variable to a number. If the variable cannot be converted, it will still become a number but with the value NaN. Mari kita lihat perilaku ini dalam sebuah tindakan

     var object = {
          name: "Sudheer",
          age: 34
     };
     
     Object literal property values can be of any data type, including array, function, and nested object.

     09

242. How do you sort elements in an array

     Metode sort() digunakan untuk mengurutkan elemen-elemen array di tempat dan mengembalikan array yang diurutkan. The example usage would be as below,

     var object = {
          name: "Sudheer",
          age: 34
     };
     
     Object literal property values can be of any data type, including array, function, and nested object.

     10

243. What is the purpose of compareFunction while sorting arrays

     The compareFunction is used to define the sort order. If omitted, the array elements are converted to strings, then sorted according to each character's Unicode code point value. Let's take an example to see the usage of compareFunction,

     var object = {
          name: "Sudheer",
          age: 34
     };
     
     Object literal property values can be of any data type, including array, function, and nested object.

     11

244. How do you reversing an array

     You can use the reverse() method to reverse the elements in an array. This method is useful to sort an array in descending order. Let's see the usage of reverse() method in an example,

     var object = {
          name: "Sudheer",
          age: 34
     };
     
     Object literal property values can be of any data type, including array, function, and nested object.

     12

245. How do you find min and max value in an array

     You can use

     // Create a new instance using function prototype.
     var newInstance = Object.create(func.prototype)
     
     // Call the function
     var result = func.call(newInstance, x, y, z),
     
     // If the result is a non-null object then use it otherwise just use the new instance.
     console.log(result && typeof result === 'object' ? result : newInstance);

     41 and

     // Create a new instance using function prototype.
     var newInstance = Object.create(func.prototype)
     
     // Call the function
     var result = func.call(newInstance, x, y, z),
     
     // If the result is a non-null object then use it otherwise just use the new instance.
     console.log(result && typeof result === 'object' ? result : newInstance);

     42 methods on array variables to find the minimum and maximum elements within an array. Let's create two functions to find the min and max value with in an array,

     var object = {
          name: "Sudheer",
          age: 34
     };
     
     Object literal property values can be of any data type, including array, function, and nested object.

     13

246. How do you find min and max values without Math functions

     You can write functions which loop through an array comparing each value with the lowest value or highest value to find the min and max values. Let's create those functions to find min and max values,

     var object = {
          name: "Sudheer",
          age: 34
     };
     
     Object literal property values can be of any data type, including array, function, and nested object.

     14

247. What is an empty statement and purpose of it

     The empty statement is a semicolon (;) indicating that no statement will be executed, even if JavaScript syntax requires one. Since there is no action with an empty statement you might think that it's usage is quite less, but the empty statement is occasionally useful when you want to create a loop that has an empty body. For example, you can initialize an array with zero values as below,

     var object = {
          name: "Sudheer",
          age: 34
     };
     
     Object literal property values can be of any data type, including array, function, and nested object.

     15

248. How do you get metadata of a module

     You can use the

     // Create a new instance using function prototype.
     var newInstance = Object.create(func.prototype)
     
     // Call the function
     var result = func.call(newInstance, x, y, z),
     
     // If the result is a non-null object then use it otherwise just use the new instance.
     console.log(result && typeof result === 'object' ? result : newInstance);

     43 object which is a meta-property exposing context-specific meta data to a JavaScript module. It contains information about the current module, such as the module's URL. In browsers, you might get different meta data than NodeJS

     var object = {
          name: "Sudheer",
          age: 34
     };
     
     Object literal property values can be of any data type, including array, function, and nested object.

     16

249. What is a comma operator

     The comma operator is used to evaluate each of its operands from left to right and returns the value of the last operand. This is totally different from comma usage within arrays, objects, and function arguments and parameters. For example, the usage for numeric expressions would be as below,

     var object = {
          name: "Sudheer",
          age: 34
     };
     
     Object literal property values can be of any data type, including array, function, and nested object.

     17

250. What is the advantage of a comma operator

     It is normally used to include multiple expressions in a location that requires a single expression. One of the common usages of this comma operator is to supply multiple parameters in a

     // Create a new instance using function prototype.
     var newInstance = Object.create(func.prototype)
     
     // Call the function
     var result = func.call(newInstance, x, y, z),
     
     // If the result is a non-null object then use it otherwise just use the new instance.
     console.log(result && typeof result === 'object' ? result : newInstance);

     44 loop. For example, the below for loop uses multiple expressions in a single location using comma operator,

     var object = {
          name: "Sudheer",
          age: 34
     };
     
     Object literal property values can be of any data type, including array, function, and nested object.

     18

     You can also use the comma operator in a return statement where it processes before returning

     var object = {
          name: "Sudheer",
          age: 34
     };
     
     Object literal property values can be of any data type, including array, function, and nested object.

     19

251. What is typescript

     TypeScript is a typed superset of JavaScript created by Microsoft that adds optional types, classes, async/await, and many other features, and compiles to plain JavaScript. Angular built entirely in TypeScript and used as a primary language. You can install it globally as

     var object = {
          name: "Sudheer",
          age: 34
     };
     
     Object literal property values can be of any data type, including array, function, and nested object.

     20

     Let's see a simple example of TypeScript usage,

     var object = {
          name: "Sudheer",
          age: 34
     };
     
     Object literal property values can be of any data type, including array, function, and nested object.

     21

     The greeting method allows only string type as argument

252. What are the differences between javascript and typescript

     Below are the list of differences between javascript and typescript,

     featuretypescriptjavascriptLanguage paradigmObject oriented programming languageScripting languageTyping supportSupports static typingIt has dynamic typingModulesSupportedNot supportedInterfaceIt has interfaces conceptDoesn't support interfacesOptional parametersFunctions support optional parametersNo support of optional parameters for functions

253. What are the advantages of typescript over javascript

     Below are some of the advantages of typescript over javascript,

     1. TypeScript is able to find compile time errors at the development time only and it makes sures less runtime errors. Whereas javascript is an interpreted language
     2. TypeScript is strongly-typed or supports static typing which allows for checking type correctness at compile time. This is not available in javascript
     3. TypeScript compiler can compile the . ts files into ES3,ES4 and ES5 unlike ES6 features of javascript which may not be supported in some browsers

254. What is an object initializer

     An object initializer is an expression that describes the initialization of an Object. The syntax for this expression is represented as a comma-delimited list of zero or more pairs of property names and associated values of an object, enclosed in curly braces ({}). This is also known as literal notation. It is one of the ways to create an object

     var object = {
          name: "Sudheer",
          age: 34
     };
     
     Object literal property values can be of any data type, including array, function, and nested object.

     22

255. What is a constructor method

     The constructor method is a special method for creating and initializing an object created within a class. If you do not specify a constructor method, a default constructor is used. The example usage of constructor would be as below,

     var object = {
          name: "Sudheer",
          age: 34
     };
     
     Object literal property values can be of any data type, including array, function, and nested object.

     23

256. What happens if you write constructor more than once in a class

     The "constructor" in a class is a special method and it should be defined only once in a class. i. e, If you write a constructor method more than once in a class it will throw a

     // Create a new instance using function prototype.
     var newInstance = Object.create(func.prototype)
     
     // Call the function
     var result = func.call(newInstance, x, y, z),
     
     // If the result is a non-null object then use it otherwise just use the new instance.
     console.log(result && typeof result === 'object' ? result : newInstance);

     45 error

     var object = {
          name: "Sudheer",
          age: 34
     };
     
     Object literal property values can be of any data type, including array, function, and nested object.

     24

257. How do you call the constructor of a parent class

     You can use the

     // Create a new instance using function prototype.
     var newInstance = Object.create(func.prototype)
     
     // Call the function
     var result = func.call(newInstance, x, y, z),
     
     // If the result is a non-null object then use it otherwise just use the new instance.
     console.log(result && typeof result === 'object' ? result : newInstance);

     46 keyword to call the constructor of a parent class. Remember that

     // Create a new instance using function prototype.
     var newInstance = Object.create(func.prototype)
     
     // Call the function
     var result = func.call(newInstance, x, y, z),
     
     // If the result is a non-null object then use it otherwise just use the new instance.
     console.log(result && typeof result === 'object' ? result : newInstance);

     47 must be called before using 'this' reference. Otherwise it will cause a reference error. Let's the usage of it,

     var object = {
          name: "Sudheer",
          age: 34
     };
     
     Object literal property values can be of any data type, including array, function, and nested object.

     25

258. How do you get the prototype of an object

     You can use the

     // Create a new instance using function prototype.
     var newInstance = Object.create(func.prototype)
     
     // Call the function
     var result = func.call(newInstance, x, y, z),
     
     // If the result is a non-null object then use it otherwise just use the new instance.
     console.log(result && typeof result === 'object' ? result : newInstance);

     48 method to return the prototype of the specified object. i. e. The value of the internal

     // Create a new instance using function prototype.
     var newInstance = Object.create(func.prototype)
     
     // Call the function
     var result = func.call(newInstance, x, y, z),
     
     // If the result is a non-null object then use it otherwise just use the new instance.
     console.log(result && typeof result === 'object' ? result : newInstance);

     11 property. If there are no inherited properties then

     // Create a new instance using function prototype.
     var newInstance = Object.create(func.prototype)
     
     // Call the function
     var result = func.call(newInstance, x, y, z),
     
     // If the result is a non-null object then use it otherwise just use the new instance.
     console.log(result && typeof result === 'object' ? result : newInstance);

     50 value is returned

     var object = {
          name: "Sudheer",
          age: 34
     };
     
     Object literal property values can be of any data type, including array, function, and nested object.

     26

259. What happens If I pass string type for getPrototype method

     In ES5, it will throw a TypeError exception if the obj parameter isn't an object. Whereas in ES2015, the parameter will be coerced to an

     // Create a new instance using function prototype.
     var newInstance = Object.create(func.prototype)
     
     // Call the function
     var result = func.call(newInstance, x, y, z),
     
     // If the result is a non-null object then use it otherwise just use the new instance.
     console.log(result && typeof result === 'object' ? result : newInstance);

     51

     var object = {
          name: "Sudheer",
          age: 34
     };
     
     Object literal property values can be of any data type, including array, function, and nested object.

     27

260. How do you set prototype of one object to another

     You can use the

     // Create a new instance using function prototype.
     var newInstance = Object.create(func.prototype)
     
     // Call the function
     var result = func.call(newInstance, x, y, z),
     
     // If the result is a non-null object then use it otherwise just use the new instance.
     console.log(result && typeof result === 'object' ? result : newInstance);

     52 method that sets the prototype (i. e. , the internal

     // Create a new instance using function prototype.
     var newInstance = Object.create(func.prototype)
     
     // Call the function
     var result = func.call(newInstance, x, y, z),
     
     // If the result is a non-null object then use it otherwise just use the new instance.
     console.log(result && typeof result === 'object' ? result : newInstance);

     53 property) of a specified object to another object or null. For example, if you want to set prototype of a square object to rectangle object would be as follows,

     var object = {
          name: "Sudheer",
          age: 34
     };
     
     Object literal property values can be of any data type, including array, function, and nested object.

     28

261. How do you check whether an object can be extendable or not

     The

     // Create a new instance using function prototype.
     var newInstance = Object.create(func.prototype)
     
     // Call the function
     var result = func.call(newInstance, x, y, z),
     
     // If the result is a non-null object then use it otherwise just use the new instance.
     console.log(result && typeof result === 'object' ? result : newInstance);

     54 method is used to determine if an object is extendable or not. i. e, Whether it can have new properties added to it or not

     var object = {
          name: "Sudheer",
          age: 34
     };
     
     Object literal property values can be of any data type, including array, function, and nested object.

     29

     Note. By default, all the objects are extendable. i. e, The new properties can be added or modified

262. How do you prevent an object to extend

     Metode

     // Create a new instance using function prototype.
     var newInstance = Object.create(func.prototype)
     
     // Call the function
     var result = func.call(newInstance, x, y, z),
     
     // If the result is a non-null object then use it otherwise just use the new instance.
     console.log(result && typeof result === 'object' ? result : newInstance);

     55 digunakan untuk mencegah properti baru ditambahkan ke objek. In other words, it prevents future extensions to the object. Let's see the usage of this property,

     var object = {
          name: "Sudheer",
          age: 34
     };
     
     Object literal property values can be of any data type, including array, function, and nested object.

     30

263. What are the different ways to make an object non-extensible

     You can mark an object non-extensible in 3 ways,

     1. Object. preventExtensions
     2. Obyek. seal
     3. Obyek. freeze

     var object = {
          name: "Sudheer",
          age: 34
     };
     
     Object literal property values can be of any data type, including array, function, and nested object.

     31

264. How do you define multiple properties on an object

     The

     // Create a new instance using function prototype.
     var newInstance = Object.create(func.prototype)
     
     // Call the function
     var result = func.call(newInstance, x, y, z),
     
     // If the result is a non-null object then use it otherwise just use the new instance.
     console.log(result && typeof result === 'object' ? result : newInstance);

     56 method is used to define new or modify existing properties directly on an object and returning the object. Let's define multiple properties on an empty object,

     var object = {
          name: "Sudheer",
          age: 34
     };
     
     Object literal property values can be of any data type, including array, function, and nested object.

     32

265. What is MEAN in javascript

     The MEAN (MongoDB, Express, AngularJS, and Node. js) stack is the most popular open-source JavaScript software tech stack available for building dynamic web apps where you can write both the server-side and client-side halves of the web project entirely in JavaScript

266. What Is Obfuscation in javascript

     Obfuscation is the deliberate act of creating obfuscated javascript code(i. e, source or machine code) that is difficult for humans to understand. It is something similar to encryption, but a machine can understand the code and execute it. Let's see the below function before Obfuscation,

     var object = {
          name: "Sudheer",
          age: 34
     };
     
     Object literal property values can be of any data type, including array, function, and nested object.

     33

     And after the code Obfuscation, it would be appeared as below,

     var object = {
          name: "Sudheer",
          age: 34
     };
     
     Object literal property values can be of any data type, including array, function, and nested object.

     34

267. Why do you need Obfuscation

     Below are the few reasons for Obfuscation,

     1. The Code size will be reduced. So data transfers between server and client will be fast
     2. It hides the business logic from outside world and protects the code from others
     3. Reverse engineering is highly difficult
     4. The download time will be reduced

268. What is Minification

     Minification is the process of removing all unnecessary characters(empty spaces are removed) and variables will be renamed without changing it's functionality. It is also a type of obfuscation

269. What are the advantages of minification

     Normally it is recommended to use minification for heavy traffic and intensive requirements of resources. It reduces file sizes with below benefits,

     1. Decreases loading times of a web page
     2. Saves bandwidth usages

270. What are the differences between Obfuscation and Encryption

     Below are the main differences between Obfuscation and Encryption,

     FeatureObfuscationEncryptionDefinitionChanging the form of any data in any other formChanging the form of information to an unreadable format by using a keyA key to decodeIt can be decoded without any keyIt is requiredTarget data formatIt will be converted to a complex formConverted into an unreadable format

271. What are the common tools used for minification

     There are many online/offline tools to minify the javascript files,

     1. Google's Closure Compiler
     2. UglifyJS2
     3. jsmin
     4. javascript-minifier. com/
     5. prettydiff. com

272. How do you perform form validation using javascript

     JavaScript can be used to perform HTML form validation. For example, if the form field is empty, the function needs to notify, and return false, to prevent the form being submitted. Lets' perform user login in an html form,

     var object = {
          name: "Sudheer",
          age: 34
     };
     
     Object literal property values can be of any data type, including array, function, and nested object.

     35

     And the validation on user login is below,

     var object = {
          name: "Sudheer",
          age: 34
     };
     
     Object literal property values can be of any data type, including array, function, and nested object.

     36

273. How do you perform form validation without javascript

     You can perform HTML form validation automatically without using javascript. The validation enabled by applying the

     // Create a new instance using function prototype.
     var newInstance = Object.create(func.prototype)
     
     // Call the function
     var result = func.call(newInstance, x, y, z),
     
     // If the result is a non-null object then use it otherwise just use the new instance.
     console.log(result && typeof result === 'object' ? result : newInstance);

     57 attribute to prevent form submission when the input is empty

     var object = {
          name: "Sudheer",
          age: 34
     };
     
     Object literal property values can be of any data type, including array, function, and nested object.

     37

     Note. Automatic form validation does not work in Internet Explorer 9 or earlier

274. What are the DOM methods available for constraint validation

     The below DOM methods are available for constraint validation on an invalid input,

     1. checkValidity(). It returns true if an input element contains valid data
     2. setCustomValidity(). It is used to set the validationMessage property of an input element. Let's take an user login form with DOM validations

     var object = {
          name: "Sudheer",
          age: 34
     };
     
     Object literal property values can be of any data type, including array, function, and nested object.

     38

275. What are the available constraint validation DOM properties

     Below are the list of some of the constraint validation DOM properties available,

     1. validity. It provides a list of boolean properties related to the validity of an input element
     2. validationMessage. It displays the message when the validity is false
     3. willValidate. It indicates if an input element will be validated or not

276. What are the list of validity properties

     The validity property of an input element provides a set of properties related to the validity of data

     1. customError. It returns true, if a custom validity message is set
     2. patternMismatch. It returns true, if an element's value does not match its pattern attribute
     3. rangeOverflow. It returns true, if an element's value is greater than its max attribute
     4. rangeUnderflow. It returns true, if an element's value is less than its min attribute
     5. stepMismatch. It returns true, if an element's value is invalid according to step attribute
     6. tooLong. It returns true, if an element's value exceeds its maxLength attribute
     7. typeMismatch. It returns true, if an element's value is invalid according to type attribute
     8. valueMissing. It returns true, if an element with a required attribute has no value
     9. valid. It returns true, if an element's value is valid

277. Give an example usage of rangeOverflow property

     If an element's value is greater than its max attribute then rangeOverflow property returns true. For example, the below form submission throws an error if the value is more than 100,

     var object = {
          name: "Sudheer",
          age: 34
     };
     
     Object literal property values can be of any data type, including array, function, and nested object.

     39

     var object = {
          name: "Sudheer",
          age: 34
     };
     
     Object literal property values can be of any data type, including array, function, and nested object.

     40

278. Is enums feature available in javascript

     No, javascript does not natively support enums. But there are different kinds of solutions to simulate them even though they may not provide exact equivalents. For example, you can use freeze or seal on object,

     var object = {
          name: "Sudheer",
          age: 34
     };
     
     Object literal property values can be of any data type, including array, function, and nested object.

     _41

279. Apa itu enum

     An enum is a type restricting variables to one value from a predefined set of constants. JavaScript has no enums but typescript provides built-in enum support

     var object = {
          name: "Sudheer",
          age: 34
     };
     
     Object literal property values can be of any data type, including array, function, and nested object.

     42

280. How do you list all properties of an object

     You can use the

     // Create a new instance using function prototype.
     var newInstance = Object.create(func.prototype)
     
     // Call the function
     var result = func.call(newInstance, x, y, z),
     
     // If the result is a non-null object then use it otherwise just use the new instance.
     console.log(result && typeof result === 'object' ? result : newInstance);

     58 method which returns an array of all properties found directly in a given object. Let's the usage of it in an example,

     var object = {
          name: "Sudheer",
          age: 34
     };
     
     Object literal property values can be of any data type, including array, function, and nested object.

     43

281. How do you get property descriptors of an object

     You can use the

     // Create a new instance using function prototype.
     var newInstance = Object.create(func.prototype)
     
     // Call the function
     var result = func.call(newInstance, x, y, z),
     
     // If the result is a non-null object then use it otherwise just use the new instance.
     console.log(result && typeof result === 'object' ? result : newInstance);

     59 method which returns all own property descriptors of a given object. The example usage of this method is below,

     var object = {
          name: "Sudheer",
          age: 34
     };
     
     Object literal property values can be of any data type, including array, function, and nested object.

     44

282. What are the attributes provided by a property descriptor

     A property descriptor is a record which has the following attributes

     1. nilai. The value associated with the property
     2. writable. Determines whether the value associated with the property can be changed or not
     3. configurable. Returns true if the type of this property descriptor can be changed and if the property can be deleted from the corresponding object
     4. enumerable. Determines whether the property appears during enumeration of the properties on the corresponding object or not
     5. set. A function which serves as a setter for the property
     6. get. A function which serves as a getter for the property

283. How do you extend classes

     The

     // Create a new instance using function prototype.
     var newInstance = Object.create(func.prototype)
     
     // Call the function
     var result = func.call(newInstance, x, y, z),
     
     // If the result is a non-null object then use it otherwise just use the new instance.
     console.log(result && typeof result === 'object' ? result : newInstance);

     60 keyword is used in class declarations/expressions to create a class which is a child of another class. It can be used to subclass custom classes as well as built-in objects. The syntax would be as below,

     var object = {
          name: "Sudheer",
          age: 34
     };
     
     Object literal property values can be of any data type, including array, function, and nested object.

     45

     Let's take an example of Square subclass from Polygon parent class,

     var object = {
          name: "Sudheer",
          age: 34
     };
     
     Object literal property values can be of any data type, including array, function, and nested object.

     25

284. How do I modify the url without reloading the page

     The

     function func() {};
     
     new func(x, y, z);

     90 property will be helpful to modify the url but it reloads the page. HTML5 introduced the

     // Create a new instance using function prototype.
     var newInstance = Object.create(func.prototype)
     
     // Call the function
     var result = func.call(newInstance, x, y, z),
     
     // If the result is a non-null object then use it otherwise just use the new instance.
     console.log(result && typeof result === 'object' ? result : newInstance);

     62 and

     // Create a new instance using function prototype.
     var newInstance = Object.create(func.prototype)
     
     // Call the function
     var result = func.call(newInstance, x, y, z),
     
     // If the result is a non-null object then use it otherwise just use the new instance.
     console.log(result && typeof result === 'object' ? result : newInstance);

     63 methods, which allow you to add and modify history entries, respectively. For example, you can use pushState as below,

     var object = {
          name: "Sudheer",
          age: 34
     };
     
     Object literal property values can be of any data type, including array, function, and nested object.

     47

285. How do you check whether an array includes a particular value or not

     The

     // Create a new instance using function prototype.
     var newInstance = Object.create(func.prototype)
     
     // Call the function
     var result = func.call(newInstance, x, y, z),
     
     // If the result is a non-null object then use it otherwise just use the new instance.
     console.log(result && typeof result === 'object' ? result : newInstance);

     64 method is used to determine whether an array includes a particular value among its entries by returning either true or false. Let's see an example to find an element(numeric and string) within an array

     var object = {
          name: "Sudheer",
          age: 34
     };
     
     Object literal property values can be of any data type, including array, function, and nested object.

     48

286. How do you compare scalar arrays

     You can use length and every method of arrays to compare two scalar(compared directly using ===) arrays. The combination of these expressions can give the expected result,

     var object = {
          name: "Sudheer",
          age: 34
     };
     
     Object literal property values can be of any data type, including array, function, and nested object.

     49

     If you would like to compare arrays irrespective of order then you should sort them before,

     var object = {
          name: "Sudheer",
          age: 34
     };
     
     Object literal property values can be of any data type, including array, function, and nested object.

     50

287. How to get the value from get parameters

     The

     // Create a new instance using function prototype.
     var newInstance = Object.create(func.prototype)
     
     // Call the function
     var result = func.call(newInstance, x, y, z),
     
     // If the result is a non-null object then use it otherwise just use the new instance.
     console.log(result && typeof result === 'object' ? result : newInstance);

     65 object accepts the url string and

     // Create a new instance using function prototype.
     var newInstance = Object.create(func.prototype)
     
     // Call the function
     var result = func.call(newInstance, x, y, z),
     
     // If the result is a non-null object then use it otherwise just use the new instance.
     console.log(result && typeof result === 'object' ? result : newInstance);

     66 property of this object can be used to access the get parameters. Remember that you may need to use polyfill or

     // Create a new instance using function prototype.
     var newInstance = Object.create(func.prototype)
     
     // Call the function
     var result = func.call(newInstance, x, y, z),
     
     // If the result is a non-null object then use it otherwise just use the new instance.
     console.log(result && typeof result === 'object' ? result : newInstance);

     67 to access the URL in older browsers(including IE)

     var object = {
          name: "Sudheer",
          age: 34
     };
     
     Object literal property values can be of any data type, including array, function, and nested object.

     51

288. How do you print numbers with commas as thousand separators

     You can use the

     // Create a new instance using function prototype.
     var newInstance = Object.create(func.prototype)
     
     // Call the function
     var result = func.call(newInstance, x, y, z),
     
     // If the result is a non-null object then use it otherwise just use the new instance.
     console.log(result && typeof result === 'object' ? result : newInstance);

     68 method which returns a string with a language-sensitive representation such as thousand separator,currency etc of this number

     var object = {
          name: "Sudheer",
          age: 34
     };
     
     Object literal property values can be of any data type, including array, function, and nested object.

     52

289. What is the difference between java and javascript

     Both are totally unrelated programming languages and no relation between them. Java is statically typed, compiled, runs on its own VM. Whereas Javascript is dynamically typed, interpreted, and runs in a browser and nodejs environments. Let's see the major differences in a tabular format,

     FeatureJavaJavaScriptTypedIt's a strongly typed languageIt's a dynamic typed languageParadigmObject oriented programmingPrototype based programmingScopingBlock scopedFunction-scopedConcurrencyThread basedevent basedMemoryUses more memoryUses less memory. Hence it will be used for web pages

290. Does JavaScript supports namespace

     JavaScript doesn’t support namespace by default. So if you create any element(function, method, object, variable) then it becomes global and pollutes the global namespace. Let's take an example of defining two functions without any namespace,

     var object = {
          name: "Sudheer",
          age: 34
     };
     
     Object literal property values can be of any data type, including array, function, and nested object.

     53

     It always calls the second function definition. Dalam hal ini, namespace akan menyelesaikan masalah tabrakan nama

291. Bagaimana Anda mendeklarasikan namespace

     Meskipun JavaScript tidak memiliki ruang nama, kita dapat menggunakan Objects , IIFE untuk membuat ruang nama

     1. Menggunakan Object Literal Notation. Mari bungkus variabel dan fungsi di dalam Object literal yang bertindak sebagai namespace. Setelah itu Anda dapat mengaksesnya menggunakan notasi objek

     var object = {
          name: "Sudheer",
          age: 34
     };
     
     Object literal property values can be of any data type, including array, function, and nested object.

     _54
     1. Menggunakan IIFE (Ekspresi fungsi yang segera dipanggil). Pasangan terluar dari tanda kurung IIFE membuat cakupan lokal untuk semua kode di dalamnya dan menjadikan fungsi anonim sebagai ekspresi fungsi. Karena itu, Anda dapat membuat fungsi yang sama dalam dua ekspresi fungsi yang berbeda untuk bertindak sebagai namespace

     var object = {
          name: "Sudheer",
          age: 34
     };
     
     Object literal property values can be of any data type, including array, function, and nested object.

     55
     1. Using a block and a let/const declaration. Di ECMAScript 6, Anda cukup menggunakan blok dan deklarasi let untuk membatasi ruang lingkup variabel ke blok

     var object = {
          name: "Sudheer",
          age: 34
     };
     
     Object literal property values can be of any data type, including array, function, and nested object.

     _56

292. Bagaimana Anda memanggil kode javascript dalam iframe dari halaman induk

     Awalnya iFrame harus diakses menggunakan

     // Create a new instance using function prototype.
     var newInstance = Object.create(func.prototype)
     
     // Call the function
     var result = func.call(newInstance, x, y, z),
     
     // If the result is a non-null object then use it otherwise just use the new instance.
     console.log(result && typeof result === 'object' ? result : newInstance);

     69 atau

     // Create a new instance using function prototype.
     var newInstance = Object.create(func.prototype)
     
     // Call the function
     var result = func.call(newInstance, x, y, z),
     
     // If the result is a non-null object then use it otherwise just use the new instance.
     console.log(result && typeof result === 'object' ? result : newInstance);

     70. Setelah itu

     // Create a new instance using function prototype.
     var newInstance = Object.create(func.prototype)
     
     // Call the function
     var result = func.call(newInstance, x, y, z),
     
     // If the result is a non-null object then use it otherwise just use the new instance.
     console.log(result && typeof result === 'object' ? result : newInstance);

     _71 properti iFrame memberikan akses untuk targetFunction

     var object = {
          name: "Sudheer",
          age: 34
     };
     
     Object literal property values can be of any data type, including array, function, and nested object.

     _57

293. Bagaimana cara mendapatkan offset zona waktu dari tanggal

     Anda dapat menggunakan metode

     // Create a new instance using function prototype.
     var newInstance = Object.create(func.prototype)
     
     // Call the function
     var result = func.call(newInstance, x, y, z),
     
     // If the result is a non-null object then use it otherwise just use the new instance.
     console.log(result && typeof result === 'object' ? result : newInstance);

     _72 dari objek tanggal. Metode ini mengembalikan perbedaan zona waktu, dalam hitungan menit, dari lokal saat ini (pengaturan sistem host) ke UTC

     var object = {
          name: "Sudheer",
          age: 34
     };
     
     Object literal property values can be of any data type, including array, function, and nested object.

     _58

294. Bagaimana Anda memuat file CSS dan JS secara dinamis

     Anda dapat membuat elemen tautan dan skrip di DOM dan menambahkannya sebagai tag anak ke kepala. Mari buat fungsi untuk menambahkan skrip dan resource gaya seperti di bawah ini,

     var object = {
          name: "Sudheer",
          age: 34
     };
     
     Object literal property values can be of any data type, including array, function, and nested object.

     _59

295. What are the different methods to find HTML elements in DOM

     Jika Anda ingin mengakses elemen apa pun di halaman HTML, Anda harus mulai dengan mengakses objek dokumen. Nanti Anda dapat menggunakan salah satu metode di bawah ini untuk menemukan elemen HTML,

     1. dokumen. getElementById(id). Ia menemukan elemen dengan Id
     2. dokumen. getElementsByTagName(nama). Ia menemukan elemen dengan nama tag
     3. dokumen. getElementsByClassName(nama). Ia menemukan elemen dengan nama kelas

296. Apa itu jQuery

     jQuery adalah pustaka JavaScript lintas-browser populer yang menyediakan penjelajahan Document Object Model (DOM), penanganan peristiwa, animasi, dan interaksi AJAX dengan meminimalkan perbedaan di seluruh browser. Ini terkenal secara luas dengan filosofi "Tulis lebih sedikit, lakukan lebih banyak". Misalnya, Anda dapat menampilkan pesan selamat datang pada pemuatan halaman menggunakan jQuery seperti di bawah ini,

     var object = {
          name: "Sudheer",
          age: 34
     };
     
     Object literal property values can be of any data type, including array, function, and nested object.

     60

     Catatan. Anda dapat mengunduhnya dari situs resmi jquery atau menginstalnya dari CDN, seperti google

297. Apa itu mesin JavaScript V8

     V8 adalah mesin JavaScript berkinerja tinggi open source yang digunakan oleh browser Google Chrome, ditulis dalam C++. Ini juga digunakan di node. proyek js. Ini mengimplementasikan ECMAScript dan WebAssembly, dan berjalan di Windows 7 atau lebih baru, macOS 10. 12+, dan sistem Linux yang menggunakan prosesor x64, IA-32, ARM, atau MIPS. Catatan. Itu dapat berjalan mandiri, atau dapat disematkan ke dalam aplikasi C ++ apa pun

298. Mengapa kami menyebut javascript sebagai bahasa dinamis

     JavaScript adalah bahasa yang diketik secara longgar atau dinamis karena variabel dalam JavaScript tidak secara langsung dikaitkan dengan jenis nilai tertentu, dan variabel apa pun dapat ditetapkan/dipindahkan dengan nilai dari semua jenis

     var object = {
          name: "Sudheer",
          age: 34
     };
     
     Object literal property values can be of any data type, including array, function, and nested object.

     _61

299. Apa itu operator batal

     Operator

     // Create a new instance using function prototype.
     var newInstance = Object.create(func.prototype)
     
     // Call the function
     var result = func.call(newInstance, x, y, z),
     
     // If the result is a non-null object then use it otherwise just use the new instance.
     console.log(result && typeof result === 'object' ? result : newInstance);

     73 mengevaluasi ekspresi yang diberikan dan kemudian mengembalikan undefined(i. e, tanpa mengembalikan nilai). Sintaksnya akan seperti di bawah ini,

     var object = {
          name: "Sudheer",
          age: 34
     };
     
     Object literal property values can be of any data type, including array, function, and nested object.

     _62

     Let's display a message without any redirection or reload

     var object = {
          name: "Sudheer",
          age: 34
     };
     
     Object literal property values can be of any data type, including array, function, and nested object.

     _63

     Catatan. Operator ini sering digunakan untuk mendapatkan nilai primitif yang tidak terdefinisi, menggunakan "void(0)"

300. Cara mengatur kursor untuk menunggu

     Kursor dapat diatur untuk menunggu di JavaScript dengan menggunakan properti "cursor". Mari kita lakukan perilaku ini saat memuat halaman menggunakan fungsi di bawah ini

     var object = {
          name: "Sudheer",
          age: 34
     };
     
     Object literal property values can be of any data type, including array, function, and nested object.

     _64

     dan fungsi ini dipanggil saat memuat halaman

     var object = {
          name: "Sudheer",
          age: 34
     };
     
     Object literal property values can be of any data type, including array, function, and nested object.

     _65

301. Bagaimana Anda membuat loop tak terbatas

     Anda dapat membuat loop tak terbatas menggunakan for dan while loop tanpa menggunakan ekspresi apa pun. Konstruksi for loop atau sintaks adalah pendekatan yang lebih baik dalam hal ESLint dan alat pengoptimal kode,

     var object = {
          name: "Sudheer",
          age: 34
     };
     
     Object literal property values can be of any data type, including array, function, and nested object.

     _66

302. Mengapa Anda perlu menghindari dengan pernyataan

     JavaScript dengan pernyataan dimaksudkan untuk memberikan singkatan untuk menulis akses berulang ke objek. Sehingga dapat membantu mengurangi ukuran file dengan mengurangi kebutuhan untuk mengulang referensi objek yang panjang tanpa penalti kinerja. Mari kita ambil contoh yang digunakan untuk menghindari redundansi saat mengakses objek beberapa kali

     var object = {
          name: "Sudheer",
          age: 34
     };
     
     Object literal property values can be of any data type, including array, function, and nested object.

     _67

     Menggunakan

     // Create a new instance using function prototype.
     var newInstance = Object.create(func.prototype)
     
     // Call the function
     var result = func.call(newInstance, x, y, z),
     
     // If the result is a non-null object then use it otherwise just use the new instance.
     console.log(result && typeof result === 'object' ? result : newInstance);

     _74 ternyata ini menjadi

     var object = {
          name: "Sudheer",
          age: 34
     };
     
     Object literal property values can be of any data type, including array, function, and nested object.

     _68

     Tapi pernyataan

     // Create a new instance using function prototype.
     var newInstance = Object.create(func.prototype)
     
     // Call the function
     var result = func.call(newInstance, x, y, z),
     
     // If the result is a non-null object then use it otherwise just use the new instance.
     console.log(result && typeof result === 'object' ? result : newInstance);

     _74 ini menciptakan masalah kinerja karena seseorang tidak dapat memprediksi apakah suatu argumen akan merujuk ke variabel nyata atau ke properti di dalam argumen with

303. Apa output dari loop di bawah ini

     var object = {
          name: "Sudheer",
          age: 34
     };
     
     Object literal property values can be of any data type, including array, function, and nested object.

     _69

     Output dari for loop di atas adalah 4 4 4 4 dan 0 1 2 3

     Penjelasan. Due to the event queue/loop of javascript, the

     // Create a new instance using function prototype.
     var newInstance = Object.create(func.prototype)
     
     // Call the function
     var result = func.call(newInstance, x, y, z),
     
     // If the result is a non-null object then use it otherwise just use the new instance.
     console.log(result && typeof result === 'object' ? result : newInstance);

     76 callback function is called after the loop has been executed. Karena variabel i dideklarasikan dengan kata kunci

     function func() {};
     
     new func(x, y, z);

     _53 itu menjadi variabel global dan nilainya sama dengan 4 menggunakan iterasi ketika fungsi

     // Create a new instance using function prototype.
     var newInstance = Object.create(func.prototype)
     
     // Call the function
     var result = func.call(newInstance, x, y, z),
     
     // If the result is a non-null object then use it otherwise just use the new instance.
     console.log(result && typeof result === 'object' ? result : newInstance);

     76 dipanggil. Oleh karena itu, output dari loop pertama adalah ________6______79

     Sedangkan pada loop kedua, variabel i dideklarasikan sebagai kata kunci

     function func() {};
     
     new func(x, y, z);

     52 itu menjadi variabel lingkup blok dan memegang nilai baru (0, 1 ,2 3) untuk setiap iterasi. Oleh karena itu, output dari loop pertama adalah ________6______81

304. Sebutkan beberapa fitur ES6

     Di bawah ini adalah daftar beberapa fitur baru ES6,

     1. Dukungan untuk konstanta atau variabel yang tidak dapat diubah
     2. Dukungan lingkup blok untuk variabel, konstanta, dan fungsi
     3. Fungsi panah
     4. Parameter bawaan
     5. Parameter Istirahat dan Penyebaran
     6. Templat Literal
     7. String multi-baris
     8. Tugas Penghancuran
     9. Literal Objek yang Disempurnakan
     10. Janji
     11. Kelas
     12. Modules

305. What is ES6

     ES6 adalah edisi keenam dari bahasa javascript dan dirilis pada Juni 2015. Awalnya dikenal sebagai ECMAScript 6 (ES6) dan kemudian berganti nama menjadi ECMAScript 2015. Hampir semua browser modern mendukung ES6 tetapi untuk browser lama ada banyak transpiler, seperti Babel. js dll

306. Bisakah saya mendeklarasikan ulang variabel let dan const

     Tidak, Anda tidak dapat mendeklarasikan ulang variabel let dan const. Jika Anda melakukannya, itu melempar kesalahan di bawah ini

     var object = {
          name: "Sudheer",
          age: 34
     };
     
     Object literal property values can be of any data type, including array, function, and nested object.

     70

     Penjelasan. Deklarasi variabel dengan kata kunci

     function func() {};
     
     new func(x, y, z);

     53 mengacu pada ruang lingkup fungsi dan variabel diperlakukan seolah-olah dideklarasikan di bagian atas ruang lingkup terlampir karena fitur pengangkat. Jadi semua beberapa deklarasi berkontribusi pada variabel yang diangkat yang sama tanpa ada kesalahan. Mari kita ambil contoh mendeklarasikan ulang variabel dalam lingkup yang sama untuk variabel var dan let/const

     var object = {
          name: "Sudheer",
          age: 34
     };
     
     Object literal property values can be of any data type, including array, function, and nested object.

     _71

     Deklarasi multi-blok melempar kesalahan sintaksis,

     var object = {
          name: "Sudheer",
          age: 34
     };
     
     Object literal property values can be of any data type, including array, function, and nested object.

     72

307. Apakah variabel const membuat nilainya tidak berubah

     Tidak, variabel const tidak membuat nilainya tidak berubah. But it disallows subsequent assignments(i. e, Anda dapat mendeklarasikan dengan penugasan tetapi tidak dapat menetapkan nilai lain nanti)

     var object = {
          name: "Sudheer",
          age: 34
     };
     
     Object literal property values can be of any data type, including array, function, and nested object.

     73

308. Apa itu parameter default

     Di E5, kita perlu bergantung pada operator logika OR untuk menangani nilai default parameter fungsi. Sedangkan di ES6, fitur parameter fungsi Default memungkinkan parameter diinisialisasi dengan nilai default jika tidak ada nilai atau undefined yang diteruskan. Mari kita bandingkan perilaku dengan contoh,

     var object = {
          name: "Sudheer",
          age: 34
     };
     
     Object literal property values can be of any data type, including array, function, and nested object.

     _74

     Parameter default membuat inisialisasi lebih sederhana,

     var object = {
          name: "Sudheer",
          age: 34
     };
     
     Object literal property values can be of any data type, including array, function, and nested object.

     75

309. Apa itu template literal

     Templat literal atau string templat adalah literal string yang memungkinkan ekspresi tersemat. Ini diapit oleh karakter back-tick (`) alih-alih tanda kutip ganda atau tunggal. Di E6, fitur ini memungkinkan penggunaan ekspresi dinamis seperti di bawah ini,

     var object = {
          name: "Sudheer",
          age: 34
     };
     
     Object literal property values can be of any data type, including array, function, and nested object.

     76

     Di ES5, Anda perlu break string seperti di bawah ini,

     var object = {
          name: "Sudheer",
          age: 34
     };
     
     Object literal property values can be of any data type, including array, function, and nested object.

     77

     Catatan. Anda dapat menggunakan string multi-baris dan fitur interpolasi string dengan literal template

310. How do you write multi-line strings in template literals

     Di ES5, Anda harus menggunakan karakter pelarian baris baru ('\n') dan simbol gabungan (+) untuk mendapatkan string multi-baris

     var object = {
          name: "Sudheer",
          age: 34
     };
     
     Object literal property values can be of any data type, including array, function, and nested object.

     78

     Sedangkan di ES6, Anda tidak perlu menyebutkan karakter urutan baris baru apa pun,

     var object = {
          name: "Sudheer",
          age: 34
     };
     
     Object literal property values can be of any data type, including array, function, and nested object.

     _79

311. Apa itu template bersarang

     Template bersarang adalah fitur yang didukung dalam sintaks literal template untuk memungkinkan backtick dalam di dalam placeholder ${ } di dalam template. Misalnya, templat bersarang di bawah ini digunakan untuk menampilkan ikon berdasarkan izin pengguna sedangkan templat luar memeriksa jenis platform,

     var object = {
          name: "Sudheer",
          age: 34
     };
     
     Object literal property values can be of any data type, including array, function, and nested object.

     _80

     Anda dapat menulis kasus penggunaan di atas tanpa fitur template bersarang juga. Namun, fitur template bersarang lebih ringkas dan mudah dibaca

     var object = {
          name: "Sudheer",
          age: 34
     };
     
     Object literal property values can be of any data type, including array, function, and nested object.

     _81

312. Apa itu template yang diberi tag

     Templat yang diberi tag adalah bentuk lanjutan dari templat di mana tag memungkinkan Anda mengurai literal templat dengan sebuah fungsi. Fungsi tag menerima parameter pertama sebagai array string dan parameter yang tersisa sebagai ekspresi. Fungsi ini juga dapat mengembalikan string yang dimanipulasi berdasarkan parameter. Mari kita lihat penggunaan perilaku templat yang diberi tag ini dari rangkaian keterampilan profesional TI dalam suatu organisasi,

     var object = {
          name: "Sudheer",
          age: 34
     };
     
     Object literal property values can be of any data type, including array, function, and nested object.

     _82

313. Apa itu string mentah

     ES6 provides a raw strings feature using the

     // Create a new instance using function prototype.
     var newInstance = Object.create(func.prototype)
     
     // Call the function
     var result = func.call(newInstance, x, y, z),
     
     // If the result is a non-null object then use it otherwise just use the new instance.
     console.log(result && typeof result === 'object' ? result : newInstance);

     83 method which is used to get the raw string form of template strings. Fitur ini memungkinkan Anda untuk mengakses string mentah saat dimasukkan, tanpa memproses urutan escape. Misalnya, penggunaannya akan seperti di bawah ini,

     var object = {
          name: "Sudheer",
          age: 34
     };
     
     Object literal property values can be of any data type, including array, function, and nested object.

     _83

     Jika Anda tidak menggunakan string mentah, urutan karakter baris baru akan diproses dengan menampilkan keluaran dalam beberapa baris

     var object = {
          name: "Sudheer",
          age: 34
     };
     
     Object literal property values can be of any data type, including array, function, and nested object.

     _84

     Juga, properti raw tersedia pada argumen pertama ke fungsi tag

     var object = {
          name: "Sudheer",
          age: 34
     };
     
     Object literal property values can be of any data type, including array, function, and nested object.

     _85

314. Apa yang merusak tugas

     Tugas penghancuran adalah ekspresi JavaScript yang memungkinkan untuk mengekstrak nilai dari array atau properti dari objek menjadi variabel yang berbeda. Mari dapatkan nilai bulan dari array menggunakan tugas destrukturisasi

     var object = {
          name: "Sudheer",
          age: 34
     };
     
     Object literal property values can be of any data type, including array, function, and nested object.

     _86

     dan Anda bisa mendapatkan properti pengguna dari suatu objek menggunakan tugas penghancuran,

     var object = {
          name: "Sudheer",
          age: 34
     };
     
     Object literal property values can be of any data type, including array, function, and nested object.

     _87

315. Apa nilai default dalam tugas penghancuran

     Variabel dapat diberi nilai default ketika nilai yang dibongkar dari larik atau objek tidak ditentukan selama penugasan destrukturisasi. Ini membantu untuk menghindari pengaturan nilai default secara terpisah untuk setiap tugas. Mari kita ambil contoh untuk kasus penggunaan array dan objek,

     Arrays destructuring

     var object = {
          name: "Sudheer",
          age: 34
     };
     
     Object literal property values can be of any data type, including array, function, and nested object.

     _88

     Penghancuran objek

     var object = {
          name: "Sudheer",
          age: 34
     };
     
     Object literal property values can be of any data type, including array, function, and nested object.

     _89

316. Bagaimana Anda menukar variabel dalam tugas penghancuran

     Jika Anda tidak menggunakan tugas penghancuran struktur, menukar dua nilai memerlukan variabel sementara. Sedangkan menggunakan fitur destrukturisasi, dua nilai variabel dapat ditukar dalam satu ekspresi destrukturisasi. Mari menukar dua variabel angka dalam tugas penghancuran array,

     var object = {
          name: "Sudheer",
          age: 34
     };
     
     Object literal property values can be of any data type, including array, function, and nested object.

     _90

317. Apa itu literal objek yang ditingkatkan

     Literal objek memudahkan pembuatan objek dengan cepat dengan properti di dalam kurung kurawal. Misalnya, ini menyediakan sintaks yang lebih pendek untuk definisi properti objek umum seperti di bawah ini

     var object = {
          name: "Sudheer",
          age: 34
     };
     
     Object literal property values can be of any data type, including array, function, and nested object.

     _91

318. Apa itu impor dinamis

     Impor dinamis menggunakan sintaks fungsi

     // Create a new instance using function prototype.
     var newInstance = Object.create(func.prototype)
     
     // Call the function
     var result = func.call(newInstance, x, y, z),
     
     // If the result is a non-null object then use it otherwise just use the new instance.
     console.log(result && typeof result === 'object' ? result : newInstance);

     _84 memungkinkan kita memuat modul sesuai permintaan dengan menggunakan promise atau sintaks async/await. Saat ini fitur ini sedang dalam proposal tahap 4. Keuntungan utama impor dinamis adalah pengurangan ukuran bundel kami, respons ukuran/muatan dari permintaan kami, dan peningkatan keseluruhan dalam pengalaman pengguna. Sintaks impor dinamis akan seperti di bawah ini,

     var object = {
          name: "Sudheer",
          age: 34
     };
     
     Object literal property values can be of any data type, including array, function, and nested object.

     92

319. Apa kasus penggunaan untuk impor dinamis

     Di bawah ini adalah beberapa kasus penggunaan impor dinamis dibandingkan impor statis,

     1. Impor modul sesuai permintaan atau kondisional. Misalnya, jika Anda ingin memuat polyfill di browser lawas

     var object = {
          name: "Sudheer",
          age: 34
     };
     
     Object literal property values can be of any data type, including array, function, and nested object.

     _93
     1. Hitung penentu modul saat runtime. Misalnya, Anda dapat menggunakannya untuk internasionalisasi

     var object = {
          name: "Sudheer",
          age: 34
     };
     
     Object literal property values can be of any data type, including array, function, and nested object.

     _94
     1. Impor modul dari dalam skrip biasa, bukan modul

320. Apa itu array yang diketik

     Array yang diketik adalah objek mirip-array dari ECMAScript 6 API untuk menangani data biner. JavaScript menyediakan 8 tipe array yang diketik,

     1. Int8Array. Array bilangan bulat bertanda 8-bit
     2. Int16Array. An array of 16-bit signed integers
     3. Int32Array. An array of 32-bit signed integers
     4. Uint8Array. An array of 8-bit unsigned integers
     5. Uint16Array. An array of 16-bit unsigned integers
     6. Uint32Array. An array of 32-bit unsigned integers
     7. Float32Array. Array angka floating point 32-bit
     8. Float64Array. Array angka floating point 64-bit

     Misalnya, Anda dapat membuat larik bilangan bulat bertanda 8-bit seperti di bawah ini

     var object = {
          name: "Sudheer",
          age: 34
     };
     
     Object literal property values can be of any data type, including array, function, and nested object.

     _95

321. Apa keuntungan dari loader modul

     Pemuat modul menyediakan fitur di bawah ini,

     1. Pemuatan dinamis
     2. State isolation
     3. Isolasi namespace global
     4. Kait kompilasi
     5. Virtualisasi bersarang

322. Apa itu pemeriksaan

     Collation digunakan untuk menyortir satu set string dan mencari dalam satu set string. Itu diparameterisasi oleh lokal dan mengetahui Unicode. Mari kita ambil fitur perbandingan dan penyortiran,

     1. Perbandingan

     var object = {
          name: "Sudheer",
          age: 34
     };
     
     Object literal property values can be of any data type, including array, function, and nested object.

     _96
     1. Penyortiran

     var object = {
          name: "Sudheer",
          age: 34
     };
     
     Object literal property values can be of any data type, including array, function, and nested object.

     _97

323. Untuk apa. pernyataan

     untuk. pernyataan membuat loop iterasi atas objek atau elemen yang dapat diubah seperti String bawaan, Array, objek mirip Array (seperti argumen atau NodeList), TypedArray, Map, Set, dan iterables yang ditentukan pengguna. Penggunaan dasar untuk. pernyataan pada array akan seperti di bawah ini,

     var object = {
          name: "Sudheer",
          age: 34
     };
     
     Object literal property values can be of any data type, including array, function, and nested object.

     _98

324. What is the output of below spread operator array

     var object = {
          name: "Sudheer",
          age: 34
     };
     
     Object literal property values can be of any data type, including array, function, and nested object.

     _99

     Output dari array adalah ['J', 'o', 'h', 'n', '', 'R', 'e', ​​'s', 'i', 'g'] Penjelasan. String adalah tipe iterable dan operator spread dalam array memetakan setiap karakter iterable ke satu elemen. Karenanya, setiap karakter string menjadi elemen di dalam Array

325. Apakah PostMessage aman

     Ya, postMessages dapat dianggap sangat aman selama pemrogram/pengembang berhati-hati dalam memeriksa asal dan sumber pesan yang datang. Tetapi jika Anda mencoba mengirim/menerima pesan tanpa memverifikasi sumbernya akan membuat serangan skrip lintas situs

326. Apa masalah dengan asal target postmessage sebagai wildcard

     Argumen kedua metode postMessage menentukan asal mana yang diizinkan untuk menerima pesan. Jika Anda menggunakan karakter pengganti “*” sebagai argumen, maka asal mana pun diizinkan untuk menerima pesan tersebut. Dalam hal ini, tidak ada cara bagi jendela pengirim untuk mengetahui apakah jendela target berada di asal target saat mengirim pesan. Jika jendela target telah dinavigasi ke Origin lain, Origin lainnya akan menerima data. Oleh karena itu, ini dapat menyebabkan kerentanan XSS

     function Person(name) {
       this.name = name;
       this.age = 21;
     }
     var object = new Person("Sudheer");

     _00

327. Bagaimana Anda menghindari menerima postMessages dari penyerang

     Karena pendengar mendengarkan pesan apa pun, penyerang dapat mengelabui aplikasi dengan mengirimkan pesan dari asal penyerang, yang memberi kesan bahwa penerima menerima pesan dari jendela pengirim yang sebenarnya. You can avoid this issue by validating the origin of the message on the receiver's end using the “message. atribut asal”. Sebagai contoh, mari kita periksa http asal pengirim. // www. beberapa pengirim. com di sisi penerima www. beberapa penerima. com,

     function Person(name) {
       this.name = name;
       this.age = 21;
     }
     var object = new Person("Sudheer");

     _01

328. Bisakah saya menghindari penggunaan postMessages sepenuhnya

     Anda tidak dapat menghindari penggunaan postMessages sepenuhnya (atau 100%). Meskipun aplikasi Anda tidak menggunakan postMessage mengingat risikonya, banyak skrip pihak ketiga menggunakan postMessage untuk berkomunikasi dengan layanan pihak ketiga. Jadi aplikasi Anda mungkin menggunakan postMessage tanpa sepengetahuan Anda

329. Apakah postMessages sinkron

     PostMessages sinkron di browser IE8 tetapi tidak sinkron di IE9 dan semua browser modern lainnya (i. e, IE9+, Firefox, Chrome, Safari). Karena perilaku asinkron ini, kami menggunakan mekanisme callback saat postMessage dikembalikan

330. Paradigma apa itu Javascript

     JavaScript adalah bahasa multi-paradigma, mendukung pemrograman imperatif/prosedural, Pemrograman Berorientasi Objek, dan pemrograman fungsional. JavaScript supports Object-Oriented Programming with prototypical inheritance

331. Apa perbedaan antara javascript internal dan eksternal

     JavaScript internal. Ini adalah kode sumber di dalam tag skrip. JavaScript eksternal. Kode sumber disimpan dalam file eksternal (disimpan dengan. js) dan dirujuk dengan dalam tag

332. Apakah JavaScript lebih cepat dari skrip sisi server

     Ya, JavaScript lebih cepat dari skrip sisi server. Karena JavaScript adalah skrip sisi klien, JavaScript tidak memerlukan bantuan server web apa pun untuk komputasi atau kalkulasinya. Jadi JavaScript selalu lebih cepat daripada skrip sisi server mana pun seperti ASP, PHP, dll

333. Bagaimana Anda mendapatkan status kotak centang

     Anda dapat menerapkan properti

     // Create a new instance using function prototype.
     var newInstance = Object.create(func.prototype)
     
     // Call the function
     var result = func.call(newInstance, x, y, z),
     
     // If the result is a non-null object then use it otherwise just use the new instance.
     console.log(result && typeof result === 'object' ? result : newInstance);

     _85 pada kotak centang yang dipilih di DOM. Jika nilainya

     // Create a new instance using function prototype.
     var newInstance = Object.create(func.prototype)
     
     // Call the function
     var result = func.call(newInstance, x, y, z),
     
     // If the result is a non-null object then use it otherwise just use the new instance.
     console.log(result && typeof result === 'object' ? result : newInstance);

     _86 berarti kotak centang dicentang jika tidak maka tidak dicentang. Misalnya, elemen kotak centang HTML di bawah ini dapat diakses menggunakan javascript seperti di bawah ini,

     function Person(name) {
       this.name = name;
       this.age = 21;
     }
     var object = new Person("Sudheer");

     _02

     function Person(name) {
       this.name = name;
       this.age = 21;
     }
     var object = new Person("Sudheer");

     _03

334. Apa tujuan dari operator tilde ganda

     The double tilde operator(~~) is known as double NOT bitwise operator. Operator ini akan menjadi pengganti Matematika yang lebih cepat. lantai()

335. Bagaimana Anda mengubah karakter menjadi kode ASCII

     Anda dapat menggunakan metode

     // Create a new instance using function prototype.
     var newInstance = Object.create(func.prototype)
     
     // Call the function
     var result = func.call(newInstance, x, y, z),
     
     // If the result is a non-null object then use it otherwise just use the new instance.
     console.log(result && typeof result === 'object' ? result : newInstance);

     _87 untuk mengubah karakter string menjadi angka ASCII. Sebagai contoh, mari cari kode ASCII untuk huruf pertama dari string 'ABC',

     function Person(name) {
       this.name = name;
       this.age = 21;
     }
     var object = new Person("Sudheer");

     _04

     Sedangkan metode

     // Create a new instance using function prototype.
     var newInstance = Object.create(func.prototype)
     
     // Call the function
     var result = func.call(newInstance, x, y, z),
     
     // If the result is a non-null object then use it otherwise just use the new instance.
     console.log(result && typeof result === 'object' ? result : newInstance);

     _88 mengonversi angka menjadi karakter ASCII yang sama

     function Person(name) {
       this.name = name;
       this.age = 21;
     }
     var object = new Person("Sudheer");

     _05

336. Apa itu ArrayBuffer

     Objek ArrayBuffer digunakan untuk merepresentasikan buffer data biner mentah dengan panjang tetap dan generik. Anda dapat membuatnya seperti di bawah ini,

     function Person(name) {
       this.name = name;
       this.age = 21;
     }
     var object = new Person("Sudheer");

     _06

     Untuk memanipulasi ArrayBuffer, kita perlu menggunakan objek "tampilan".

     function Person(name) {
       this.name = name;
       this.age = 21;
     }
     var object = new Person("Sudheer");

     _07

337. Apa output dari ekspresi string di bawah ini

     function Person(name) {
       this.name = name;
       this.age = 21;
     }
     var object = new Person("Sudheer");

     _08

     Output dari ekspresi di atas adalah "W". Penjelasan. The bracket notation with specific index on a string returns the character at a specific location. Oleh karena itu, mengembalikan karakter "W" dari string. Karena ini tidak didukung di IE7 dan versi di bawahnya, Anda mungkin perlu menggunakan. metode charAt() untuk mendapatkan hasil yang diinginkan

338. Apa tujuan dari objek Error

     Konstruktor Error membuat objek error dan instance objek error dilempar saat error runtime terjadi. Objek Error juga dapat digunakan sebagai objek dasar untuk pengecualian yang ditentukan pengguna. Sintaks objek kesalahan akan seperti di bawah ini,

     function Person(name) {
       this.name = name;
       this.age = 21;
     }
     var object = new Person("Sudheer");

     _09

     Anda dapat membuang pengecualian atau kesalahan yang ditentukan pengguna menggunakan objek Kesalahan dalam percobaan. menangkap blok seperti di bawah ini,

     function Person(name) {
       this.name = name;
       this.age = 21;
     }
     var object = new Person("Sudheer");

     _10

339. Apa tujuan dari objek EvalError

     Objek EvalError menunjukkan kesalahan terkait fungsi

     // Create a new instance using function prototype.
     var newInstance = Object.create(func.prototype)
     
     // Call the function
     var result = func.call(newInstance, x, y, z),
     
     // If the result is a non-null object then use it otherwise just use the new instance.
     console.log(result && typeof result === 'object' ? result : newInstance);

     89 global. Meskipun pengecualian ini tidak lagi dilemparkan oleh JavaScript, objek EvalError tetap untuk kompatibilitas. Sintaks ekspresi ini akan seperti di bawah ini,

     function Person(name) {
       this.name = name;
       this.age = 21;
     }
     var object = new Person("Sudheer");

     _11

     Anda dapat melempar EvalError dengan mencoba. menangkap blok seperti di bawah ini,

     function Person(name) {
       this.name = name;
       this.age = 21;
     }
     var object = new Person("Sudheer");

     12

340. What are the list of cases error thrown from non-strict mode to strict mode

     Saat Anda menerapkan 'gunakan ketat';

     1. Saat Anda menggunakan sintaks Oktal

     function Person(name) {
       this.name = name;
       this.age = 21;
     }
     var object = new Person("Sudheer");

     _13
     1. Menggunakan

        // Create a new instance using function prototype.
        var newInstance = Object.create(func.prototype)
        
        // Call the function
        var result = func.call(newInstance, x, y, z),
        
        // If the result is a non-null object then use it otherwise just use the new instance.
        console.log(result && typeof result === 'object' ? result : newInstance);

        _74 pernyataan
     2. Saat Anda menggunakan operator hapus pada nama variabel
     3. Menggunakan eval atau argumen sebagai nama argumen variabel atau fungsi
     4. Saat Anda menggunakan kata kunci yang baru dipesan
     5. Saat Anda mendeklarasikan fungsi di blok

     function Person(name) {
       this.name = name;
       this.age = 21;
     }
     var object = new Person("Sudheer");

     _14

     Karenanya, kesalahan dari kasus di atas sangat membantu untuk menghindari kesalahan dalam lingkungan pengembangan/produksi

341. Apakah semua objek memiliki prototipe

     TIDAK. Semua objek memiliki prototipe kecuali objek dasar yang dibuat oleh pengguna, atau objek yang dibuat menggunakan kata kunci baru

342. Apa perbedaan antara parameter dan argumen

     Parameter adalah nama variabel dari definisi fungsi sedangkan argumen mewakili nilai yang diberikan ke fungsi saat dipanggil. Mari kita jelaskan ini dengan fungsi sederhana

     function Person(name) {
       this.name = name;
       this.age = 21;
     }
     var object = new Person("Sudheer");

     _15

343. Apa tujuan dari beberapa metode dalam array

     The some() method is used to test whether at least one element in the array passes the test implemented by the provided function. Metode mengembalikan nilai boolean. Mari kita ambil contoh untuk menguji elemen ganjil,

     function Person(name) {
       this.name = name;
       this.age = 21;
     }
     var object = new Person("Sudheer");

     _16

344. Bagaimana Anda menggabungkan dua atau lebih array

     Metode concat() digunakan untuk menggabungkan dua atau lebih array dengan mengembalikan array baru yang berisi semua elemen. Sintaksnya akan seperti di bawah ini,

     function Person(name) {
       this.name = name;
       this.age = 21;
     }
     var object = new Person("Sudheer");

     _17

     Mari kita ambil contoh rangkaian array dengan array sayuran dan buah-buahan,

     function Person(name) {
       this.name = name;
       this.age = 21;
     }
     var object = new Person("Sudheer");

     _18

345. Apa perbedaan antara salinan Dangkal dan Dalam

     Ada dua cara untuk menyalin objek,

     Salinan dangkal. Salinan dangkal adalah salinan bitwise dari suatu objek. Objek baru dibuat yang memiliki salinan persis dari nilai-nilai di objek asli. Jika salah satu bidang objek adalah referensi ke objek lain, hanya alamat referensi yang disalin i. e. , hanya alamat memori yang disalin

     Contoh

     function Person(name) {
       this.name = name;
       this.age = 21;
     }
     var object = new Person("Sudheer");

     19

     untuk membuat duplikat

     function Person(name) {
       this.name = name;
       this.age = 21;
     }
     var object = new Person("Sudheer");

     _20

     jika kita mengubah beberapa nilai properti di duplikat seperti ini

     function Person(name) {
       this.name = name;
       this.age = 21;
     }
     var object = new Person("Sudheer");

     _21

     Pernyataan di atas juga akan mengubah nama

     // Create a new instance using function prototype.
     var newInstance = Object.create(func.prototype)
     
     // Call the function
     var result = func.call(newInstance, x, y, z),
     
     // If the result is a non-null object then use it otherwise just use the new instance.
     console.log(result && typeof result === 'object' ? result : newInstance);

     91, karena kita memiliki salinan yang dangkal. Itu berarti kami juga kehilangan data aslinya

     Salinan yang dalam. Salinan dalam menyalin semua bidang, dan membuat salinan memori yang dialokasikan secara dinamis yang ditunjukkan oleh bidang. Salinan yang dalam terjadi ketika sebuah objek disalin bersama dengan objek yang dirujuknya

     Contoh

     function Person(name) {
       this.name = name;
       this.age = 21;
     }
     var object = new Person("Sudheer");

     19

     Buat salinan dalam dengan menggunakan properti dari objek asli ke dalam variabel baru

     function Person(name) {
       this.name = name;
       this.age = 21;
     }
     var object = new Person("Sudheer");

     _23

     Sekarang jika Anda mengubah

     // Create a new instance using function prototype.
     var newInstance = Object.create(func.prototype)
     
     // Call the function
     var result = func.call(newInstance, x, y, z),
     
     // If the result is a non-null object then use it otherwise just use the new instance.
     console.log(result && typeof result === 'object' ? result : newInstance);

     _92, itu hanya akan mempengaruhi

     // Create a new instance using function prototype.
     var newInstance = Object.create(func.prototype)
     
     // Call the function
     var result = func.call(newInstance, x, y, z),
     
     // If the result is a non-null object then use it otherwise just use the new instance.
     console.log(result && typeof result === 'object' ? result : newInstance);

     93 & bukan

     // Create a new instance using function prototype.
     var newInstance = Object.create(func.prototype)
     
     // Call the function
     var result = func.call(newInstance, x, y, z),
     
     // If the result is a non-null object then use it otherwise just use the new instance.
     console.log(result && typeof result === 'object' ? result : newInstance);

     91

346. Bagaimana Anda membuat sejumlah salinan tertentu dari sebuah string

     Metode

     // Create a new instance using function prototype.
     var newInstance = Object.create(func.prototype)
     
     // Call the function
     var result = func.call(newInstance, x, y, z),
     
     // If the result is a non-null object then use it otherwise just use the new instance.
     console.log(result && typeof result === 'object' ? result : newInstance);

     95 digunakan untuk membuat dan mengembalikan string baru yang berisi jumlah salinan string yang telah ditentukan yang disebutnya, digabungkan menjadi satu. Ingatlah bahwa metode ini telah ditambahkan ke spesifikasi ECMAScript 2015. Mari kita ambil contoh string Hello untuk mengulanginya 4 kali,

     function Person(name) {
       this.name = name;
       this.age = 21;
     }
     var object = new Person("Sudheer");

     _24

347. How do you return all matching strings against a regular expression

     Metode

     // Create a new instance using function prototype.
     var newInstance = Object.create(func.prototype)
     
     // Call the function
     var result = func.call(newInstance, x, y, z),
     
     // If the result is a non-null object then use it otherwise just use the new instance.
     console.log(result && typeof result === 'object' ? result : newInstance);

     96 dapat digunakan untuk mengembalikan iterator dari semua hasil yang cocok dengan string terhadap ekspresi reguler. Misalnya, contoh di bawah mengembalikan larik hasil string yang cocok dengan ekspresi reguler,

     function Person(name) {
       this.name = name;
       this.age = 21;
     }
     var object = new Person("Sudheer");

     _25

348. Bagaimana Anda memangkas string di awal atau akhir

     Metode prototipe string ________6______97 digunakan untuk memangkas kedua sisi string. Tetapi jika Anda ingin memangkas terutama di awal atau akhir string maka Anda dapat menggunakan metode

     // Create a new instance using function prototype.
     var newInstance = Object.create(func.prototype)
     
     // Call the function
     var result = func.call(newInstance, x, y, z),
     
     // If the result is a non-null object then use it otherwise just use the new instance.
     console.log(result && typeof result === 'object' ? result : newInstance);

     98 dan

     // Create a new instance using function prototype.
     var newInstance = Object.create(func.prototype)
     
     // Call the function
     var result = func.call(newInstance, x, y, z),
     
     // If the result is a non-null object then use it otherwise just use the new instance.
     console.log(result && typeof result === 'object' ? result : newInstance);

     99. Mari kita lihat contoh metode ini pada pesan ucapan,

     function Person(name) {
       this.name = name;
       this.age = 21;
     }
     var object = new Person("Sudheer");

     _26

349. Apa output dari pernyataan konsol di bawah ini dengan operator unary

     Mari kita ambil pernyataan konsol dengan operator unary seperti yang diberikan di bawah ini,

     function Person(name) {
       this.name = name;
       this.age = 21;
     }
     var object = new Person("Sudheer");

     _27

     Output dari pernyataan log konsol di atas mengembalikan NaN. Karena elemen tersebut diawali oleh operator unary dan juru bahasa JavaScript akan mencoba mengubah elemen tersebut menjadi tipe angka. Karena konversi gagal, nilai pernyataan menghasilkan nilai NaN

350. Apakah javascript menggunakan mixin

     Mixin adalah istilah pemrograman berorientasi objek generik - adalah kelas yang berisi metode yang dapat digunakan oleh kelas lain tanpa perlu mewarisinya. Dalam JavaScript kita hanya dapat mewarisi dari satu objek. yaitu. There can be only one

     class Person {
       constructor(name) {
         this.name = name;
       }
     }
     
     var object = new Person("Sudheer");

     00 for an object

     Tapi terkadang kita perlu memperluas lebih dari satu, untuk mengatasinya kita bisa menggunakan Mixin yang membantu menyalin metode ke prototipe kelas lain

     Misalnya, kita memiliki dua kelas

     class Person {
       constructor(name) {
         this.name = name;
       }
     }
     
     var object = new Person("Sudheer");

     01 dan

     class Person {
       constructor(name) {
         this.name = name;
       }
     }
     
     var object = new Person("Sudheer");

     02. Misalkan kita perlu menambahkan fungsionalitas

     class Person {
       constructor(name) {
         this.name = name;
       }
     }
     
     var object = new Person("Sudheer");

     _02 ke

     class Person {
       constructor(name) {
         this.name = name;
       }
     }
     
     var object = new Person("Sudheer");

     01, sehingga pengguna dapat membersihkan ruangan sesuai permintaan. Di sinilah konsep yang disebut mixin muncul

     function Person(name) {
       this.name = name;
       this.age = 21;
     }
     var object = new Person("Sudheer");

     _28

351. Apa itu fungsi thunk

     Thunk hanyalah sebuah fungsi yang menunda evaluasi nilai. Itu tidak membutuhkan argumen apa pun tetapi memberikan nilai setiap kali Anda memanggil thunk. Saya. e, Ini digunakan untuk tidak mengeksekusi sekarang tetapi suatu saat nanti. Mari kita ambil contoh sinkron,

     function Person(name) {
       this.name = name;
       this.age = 21;
     }
     var object = new Person("Sudheer");

     _29

352. Apa itu pemikiran asinkron

     Thunk asinkron berguna untuk membuat permintaan jaringan. Mari kita lihat contoh permintaan jaringan,

     function Person(name) {
       this.name = name;
       this.age = 21;
     }
     var object = new Person("Sudheer");

     _30

     Fungsi

     class Person {
       constructor(name) {
         this.name = name;
       }
     }
     
     var object = new Person("Sudheer");

     _05 tidak akan langsung dipanggil tetapi hanya akan dipanggil jika data tersedia dari titik akhir API. Fungsi setTimeout juga digunakan untuk membuat kode kita tidak sinkron. Contoh waktu nyata terbaik adalah redux state management library yang menggunakan asynchronous thunks untuk menunda tindakan pengiriman

353. Apa output dari pemanggilan fungsi di bawah ini

     Cuplikan kode

     function Person(name) {
       this.name = name;
       this.age = 21;
     }
     var object = new Person("Sudheer");

     _31

     function Person(name) {
       this.name = name;
       this.age = 21;
     }
     var object = new Person("Sudheer");

     _32

     Keluaran

     Outputnya adalah 40 dan NaN. Ingatlah bahwa diameter adalah fungsi biasa, sedangkan nilai keliling adalah fungsi panah. The

     function func() {};
     
     new func(x, y, z);

     48 keyword of a regular function(i. e, diameter) refers to the surrounding scope which is a class(i. e, Bentuk objek). Sedangkan kata kunci fungsi perimeter ini mengacu pada ruang lingkup sekitarnya yang merupakan objek jendela. Karena tidak ada properti radius pada objek jendela, ia mengembalikan nilai yang tidak ditentukan dan kelipatan nilai angka mengembalikan nilai NaN

354. Cara menghapus semua jeda baris dari sebuah string

     Pendekatan termudah adalah menggunakan ekspresi reguler untuk mendeteksi dan mengganti baris baru dalam string. Dalam hal ini, kami menggunakan fungsi ganti bersama dengan string untuk mengganti, yang dalam kasus kami adalah string kosong

     function Person(name) {
       this.name = name;
       this.age = 21;
     }
     var object = new Person("Sudheer");

     _33

     Pada ekspresi di atas, g dan m adalah untuk flag global dan multiline

355. Apa perbedaan antara reflow dan repaint

     Pengecatan ulang terjadi ketika perubahan dibuat yang memengaruhi visibilitas elemen, tetapi bukan tata letaknya. Contohnya termasuk garis besar, visibilitas, atau warna latar belakang. Reflow melibatkan perubahan yang memengaruhi tata letak sebagian halaman (atau seluruh halaman). Mengubah ukuran jendela browser, mengubah font, mengubah konten (seperti teks yang diketik pengguna), menggunakan metode JavaScript yang melibatkan gaya terkomputasi, menambah atau menghapus elemen dari DOM, dan mengubah kelas elemen adalah beberapa hal yang dapat memicu reflow. Reflow suatu elemen menyebabkan reflow berikutnya dari semua elemen anak dan elemen leluhur serta elemen apa pun yang mengikutinya di DOM

356. Apa yang terjadi dengan meniadakan array

     Meniadakan array dengan

     class Person {
       constructor(name) {
         this.name = name;
       }
     }
     
     var object = new Person("Sudheer");

     07 karakter akan memaksa array menjadi boolean. Karena Array dianggap benar Jadi meniadakannya akan mengembalikan

     class Person {
       constructor(name) {
         this.name = name;
       }
     }
     
     var object = new Person("Sudheer");

     08

     function Person(name) {
       this.name = name;
       this.age = 21;
     }
     var object = new Person("Sudheer");

     34

357. Apa yang terjadi jika kita menambahkan dua array

     Jika Anda menambahkan dua larik bersama, itu akan mengonversi keduanya menjadi string dan menggabungkannya. Misalnya, hasil penambahan array akan seperti di bawah ini,

     function Person(name) {
       this.name = name;
       this.age = 21;
     }
     var object = new Person("Sudheer");

     _35

358. Apa output dari menambahkan operator tambahan pada nilai-nilai palsu

     Jika Anda menambahkan operator aditif(+) pada nilai palsu (null, undefined, NaN, false, ""), nilai palsu dikonversi menjadi angka bernilai nol. Mari kita tampilkan di konsol browser seperti di bawah ini,

     function Person(name) {
       this.name = name;
       this.age = 21;
     }
     var object = new Person("Sudheer");

     _36

359. Bagaimana Anda membuat string sendiri menggunakan karakter khusus

     String diri dapat dibentuk dengan kombinasi

     class Person {
       constructor(name) {
         this.name = name;
       }
     }
     
     var object = new Person("Sudheer");

     09 karakter. Anda perlu mengingat konvensi di bawah ini untuk mencapai pola ini
     1. Karena Array adalah nilai yang benar, meniadakan array akan menghasilkan false. . [] === salah
     2. Sesuai aturan pemaksaan JavaScript, penambahan array bersama-sama akan meringkasnya. [] + [] === ""
     3. Tambahkan array dengan + operator akan mengubah array menjadi false, negasi akan menjadikannya benar dan akhirnya mengonversi hasilnya akan menghasilkan nilai '1'. +(. (+[])) === 1

     Dengan menerapkan aturan di atas, kita dapat memperoleh kondisi di bawah ini

     function Person(name) {
       this.name = name;
       this.age = 21;
     }
     var object = new Person("Sudheer");

     _37

     Sekarang pola karakter akan dibuat seperti di bawah ini,

     function Person(name) {
       this.name = name;
       this.age = 21;
     }
     var object = new Person("Sudheer");

     _38

360. Bagaimana Anda menghapus nilai-nilai palsu dari sebuah array

     Anda dapat menerapkan metode filter pada array dengan meneruskan Boolean sebagai parameter. Dengan cara ini menghapus semua nilai falsy(0, undefined, null, false dan "") dari array

     function Person(name) {
       this.name = name;
       this.age = 21;
     }
     var object = new Person("Sudheer");

     _39

361. Bagaimana Anda mendapatkan nilai unik dari sebuah array

     Anda bisa mendapatkan nilai unik dari sebuah array dengan kombinasi

     class Person {
       constructor(name) {
         this.name = name;
       }
     }
     
     var object = new Person("Sudheer");

     10 dan rest expression/spread(. ) sintaks

     function Person(name) {
       this.name = name;
       this.age = 21;
     }
     var object = new Person("Sudheer");

     _40

362. Apa yang merusak alias

     Terkadang Anda ingin memiliki variabel yang didestrukturisasi dengan nama yang berbeda dari nama properti. Dalam hal ini, Anda akan menggunakan

     class Person {
       constructor(name) {
         this.name = name;
       }
     }
     
     var object = new Person("Sudheer");

     _11 untuk menentukan nama variabel. Proses ini disebut alias penghancuran

     function Person(name) {
       this.name = name;
       this.age = 21;
     }
     var object = new Person("Sudheer");

     _41

363. How do you map the array values without using map method

     Anda dapat memetakan nilai array tanpa menggunakan metode

     class Person {
       constructor(name) {
         this.name = name;
       }
     }
     
     var object = new Person("Sudheer");

     12 dengan hanya menggunakan metode

     class Person {
       constructor(name) {
         this.name = name;
       }
     }
     
     var object = new Person("Sudheer");

     13 dari Array. Mari petakan nama kota dari larik Negara,

     function Person(name) {
       this.name = name;
       this.age = 21;
     }
     var object = new Person("Sudheer");

     _42

364. Bagaimana Anda mengosongkan array

     Anda dapat mengosongkan array dengan cepat dengan menyetel panjang array ke nol

     function Person(name) {
       this.name = name;
       this.age = 21;
     }
     var object = new Person("Sudheer");

     _43

365. Bagaimana cara membulatkan angka ke desimal tertentu

     Anda dapat membulatkan angka ke angka desimal tertentu menggunakan metode

     class Person {
       constructor(name) {
         this.name = name;
       }
     }
     
     var object = new Person("Sudheer");

     14 dari javascript asli

     function Person(name) {
       this.name = name;
       this.age = 21;
     }
     var object = new Person("Sudheer");

     _44

366. Apa cara termudah untuk mengubah array menjadi objek

     Anda dapat mengonversi array menjadi objek dengan data yang sama menggunakan spread(. ) operator

     function Person(name) {
       this.name = name;
       this.age = 21;
     }
     var object = new Person("Sudheer");

     _45

367. Bagaimana Anda membuat array dengan beberapa data

     Anda dapat membuat larik dengan beberapa data atau larik dengan nilai yang sama menggunakan metode

     class Person {
       constructor(name) {
         this.name = name;
       }
     }
     
     var object = new Person("Sudheer");

     15

     function Person(name) {
       this.name = name;
       this.age = 21;
     }
     var object = new Person("Sudheer");

     _46

368. Apa placeholder dari objek konsol

     Di bawah ini adalah daftar placeholder yang tersedia dari objek konsol,

     1. %o — It takes an object,
     2. %s — Dibutuhkan sebuah string,
     3. %d — Digunakan untuk desimal atau bilangan bulat Tempat penampung ini dapat direpresentasikan di konsol. log seperti di bawah ini

     function Person(name) {
       this.name = name;
       this.age = 21;
     }
     var object = new Person("Sudheer");

     _47

369. Apakah mungkin menambahkan CSS ke pesan konsol

     Ya, Anda dapat menerapkan gaya CSS ke pesan konsol yang mirip dengan teks html di halaman web

     function Person(name) {
       this.name = name;
       this.age = 21;
     }
     var object = new Person("Sudheer");

     _48

     Teks akan ditampilkan seperti di bawah ini,

     

     Catatan. Semua gaya CSS dapat diterapkan ke pesan konsol

370. Apa tujuan dari metode dir dari objek konsol

     class Person {
       constructor(name) {
         this.name = name;
       }
     }
     
     var object = new Person("Sudheer");

     _16 digunakan untuk menampilkan daftar interaktif properti objek JavaScript yang ditentukan sebagai JSON

     function Person(name) {
       this.name = name;
       this.age = 21;
     }
     var object = new Person("Sudheer");

     _49

     Objek pengguna ditampilkan dalam representasi JSON

     

371. Apakah mungkin untuk men-debug elemen HTML di konsol

     Ya, adalah mungkin untuk mendapatkan dan men-debug elemen HTML di konsol seperti halnya memeriksa elemen

     function Person(name) {
       this.name = name;
       this.age = 21;
     }
     var object = new Person("Sudheer");

     _50

     Itu mencetak elemen HTML di konsol,

     

372. How do you display data in a tabular format using console object

     class Person {
       constructor(name) {
         this.name = name;
       }
     }
     
     var object = new Person("Sudheer");

     _17 digunakan untuk menampilkan data di konsol dalam format tabel untuk memvisualisasikan array atau objek yang kompleks

     function Person(name) {
       this.name = name;
       this.age = 21;
     }
     var object = new Person("Sudheer");

     _51

     Data divisualisasikan dalam format tabel,

     
     Bukan. Ingatlah bahwa

     class Person {
       constructor(name) {
         this.name = name;
       }
     }
     
     var object = new Person("Sudheer");

     _17 tidak didukung di IE

373. Bagaimana Anda memverifikasi bahwa argumen adalah Angka atau bukan

     Kombinasi metode IsNaN dan isFinite digunakan untuk mengonfirmasi apakah suatu argumen berupa angka atau bukan

     function Person(name) {
       this.name = name;
       this.age = 21;
     }
     var object = new Person("Sudheer");

     _52

374. Bagaimana Anda membuat tombol salin ke clipboard

     Anda perlu memilih konten (menggunakan. pilih () metode) dari elemen input dan jalankan perintah salin dengan execCommand (i. e, execCommand('salin')). Anda juga dapat menjalankan perintah sistem lainnya seperti potong dan tempel

     function Person(name) {
       this.name = name;
       this.age = 21;
     }
     var object = new Person("Sudheer");

     _53

375. Apa jalan pintas untuk mendapatkan stempel waktu

     Anda dapat menggunakan

     class Person {
       constructor(name) {
         this.name = name;
       }
     }
     
     var object = new Person("Sudheer");

     19 untuk mendapatkan stempel waktu saat ini. Ada jalan pintas alternatif untuk mendapatkan nilai

     function Person(name) {
       this.name = name;
       this.age = 21;
     }
     var object = new Person("Sudheer");

     _54

376. Bagaimana Anda meratakan array multi dimensi

     Meratakan array dua dimensi itu sepele dengan operator Spread

     function Person(name) {
       this.name = name;
       this.age = 21;
     }
     var object = new Person("Sudheer");

     _55

     Tapi Anda bisa membuatnya bekerja dengan array multidimensi dengan panggilan rekursif,

     function Person(name) {
       this.name = name;
       this.age = 21;
     }
     var object = new Person("Sudheer");

     _56

     Anda juga dapat menggunakan metode Array

     class Person {
       constructor(name) {
         this.name = name;
       }
     }
     
     var object = new Person("Sudheer");

     _20

     function Person(name) {
       this.name = name;
       this.age = 21;
     }
     var object = new Person("Sudheer");

     57

377. What is the easiest multi condition checking

     Anda dapat menggunakan

     class Person {
       constructor(name) {
         this.name = name;
       }
     }
     
     var object = new Person("Sudheer");

     21 untuk membandingkan input dengan banyak nilai alih-alih memeriksa setiap nilai sebagai satu syarat

     function Person(name) {
       this.name = name;
       this.age = 21;
     }
     var object = new Person("Sudheer");

     _58

378. Bagaimana Anda menangkap tombol kembali browser

     Metode

     class Person {
       constructor(name) {
         this.name = name;
       }
     }
     
     var object = new Person("Sudheer");

     _22 digunakan untuk merekam peristiwa tombol kembali browser. Ini berguna untuk memperingatkan pengguna tentang kehilangan data saat ini

     function Person(name) {
       this.name = name;
       this.age = 21;
     }
     var object = new Person("Sudheer");

     _59

379. Bagaimana Anda menonaktifkan klik kanan di halaman web

     Klik kanan pada halaman dapat dinonaktifkan dengan mengembalikan false dari atribut

     class Person {
       constructor(name) {
         this.name = name;
       }
     }
     
     var object = new Person("Sudheer");

     23 pada elemen body

     function Person(name) {
       this.name = name;
       this.age = 21;
     }
     var object = new Person("Sudheer");

     _60

380. Apa itu objek pembungkus

     Nilai Primitif seperti string, angka, dan boolean tidak memiliki properti dan metode tetapi untuk sementara dikonversi atau dipaksa menjadi objek (objek Pembungkus) saat Anda mencoba melakukan tindakan terhadapnya. Misalnya, jika Anda menerapkan metode toUpperCase() pada nilai string primitif, itu tidak menimbulkan kesalahan tetapi mengembalikan huruf besar dari string

     function Person(name) {
       this.name = name;
       this.age = 21;
     }
     var object = new Person("Sudheer");

     _61

     i. e, Setiap primitif kecuali nol dan tidak terdefinisi memiliki Objek Pembungkus dan daftar objek pembungkus adalah String, Angka, Boolean, Simbol, dan BigInt

381. Apa itu AJAX

     AJAX adalah singkatan dari Asynchronous JavaScript and XML dan itu adalah sekelompok teknologi terkait (HTML, CSS, JavaScript, XMLHttpRequest API dll) yang digunakan untuk menampilkan data secara asinkron. Saya. e. We can send data to the server and get data from the server without reloading the web page

382. Apa saja cara berbeda untuk menangani Kode Asinkron

     Di bawah ini adalah daftar berbagai cara untuk menangani kode Asinkron

     1. Panggilan balik
     2. Janji
     3. Asinkron/menunggu
     4. Pustaka pihak ketiga seperti async. js, bluebird dll

383. Cara membatalkan permintaan pengambilan

     Sampai beberapa hari yang lalu, satu kekurangan dari native promise adalah tidak ada cara langsung untuk membatalkan permintaan pengambilan. Tapi

     class Person {
       constructor(name) {
         this.name = name;
       }
     }
     
     var object = new Person("Sudheer");

     24 baru dari spesifikasi js memungkinkan Anda menggunakan sinyal untuk membatalkan satu atau beberapa panggilan pengambilan. Alur dasar pembatalan permintaan pengambilan adalah seperti di bawah ini,
     1. Buat instance

        class Person {
          constructor(name) {
            this.name = name;
          }
        }
        
        var object = new Person("Sudheer");

        _24
     2. Dapatkan properti sinyal dari sebuah instance dan teruskan sinyal sebagai opsi pengambilan untuk sinyal
     3. Panggil properti abort dari AbortController untuk membatalkan semua pengambilan yang menggunakan sinyal tersebut. Sebagai contoh, mari berikan sinyal yang sama ke beberapa panggilan pengambilan yang akan membatalkan semua permintaan dengan sinyal tersebut,

     function Person(name) {
       this.name = name;
       this.age = 21;
     }
     var object = new Person("Sudheer");

     _62

384. Apa itu API ucapan web

     API ucapan web digunakan untuk memungkinkan browser modern mengenali dan mensintesis ucapan (i. e, data suara ke dalam aplikasi web). API ini telah diperkenalkan oleh Komunitas W3C pada tahun 2012. It has two main parts,

     1. SpeechRecognition (Pengenalan Ucapan Asynchronous atau Speech-to-Text). Ini memberikan kemampuan untuk mengenali konteks suara dari input audio dan meresponsnya dengan sesuai. Ini diakses oleh antarmuka

        class Person {
          constructor(name) {
            this.name = name;
          }
        }
        
        var object = new Person("Sudheer");

        _26. Contoh di bawah ini menunjukkan cara menggunakan API ini untuk mendapatkan teks dari ucapan,

     function Person(name) {
       this.name = name;
       this.age = 21;
     }
     var object = new Person("Sudheer");

     _63

     Di API ini, browser akan meminta izin Anda untuk menggunakan mikrofon Anda

     1. Sintesis Pidato (Teks-ke-Ucapan). Ini memberikan kemampuan untuk mengenali konteks suara dari input audio dan merespons. Ini diakses oleh antarmuka

        class Person {
          constructor(name) {
            this.name = name;
          }
        }
        
        var object = new Person("Sudheer");

        _27. Misalnya, kode di bawah ini digunakan untuk mendapatkan suara/ucapan dari teks,

     function Person(name) {
       this.name = name;
       this.age = 21;
     }
     var object = new Person("Sudheer");

     _64

     Contoh di atas dapat diuji pada konsol pengembang browser chrome(33+). Catatan. API ini masih berupa draft kerja dan hanya tersedia di browser Chrome dan Firefox (tentu saja Chrome hanya mengimplementasikan spesifikasinya)

385. Apa itu pelambatan batas waktu minimum

     Lingkungan javascript browser dan NodeJS melambat dengan penundaan minimum yang lebih besar dari 0 md. Artinya walaupun setting delay 0ms tidak akan terjadi secara instan. Browsers. Mereka memiliki penundaan minimal 4ms. Throttle ini terjadi ketika panggilan berturut-turut dipicu karena callback nesting (kedalaman tertentu) atau setelah sejumlah interval berturut-turut. Catatan. Browser lama memiliki penundaan minimal 10ms. Nodejs. Mereka memiliki penundaan minimal 1ms. Throttle ini terjadi ketika penundaan lebih besar dari 2147483647 atau kurang dari 1. Contoh terbaik untuk menjelaskan perilaku pelambatan batas waktu ini adalah urutan cuplikan kode di bawah ini

     function Person(name) {
       this.name = name;
       this.age = 21;
     }
     var object = new Person("Sudheer");

     _65

     dan output akan masuk

     function Person(name) {
       this.name = name;
       this.age = 21;
     }
     var object = new Person("Sudheer");

     _66

     Jika Anda tidak menggunakan

     // Create a new instance using function prototype.
     var newInstance = Object.create(func.prototype)
     
     // Call the function
     var result = func.call(newInstance, x, y, z),
     
     // If the result is a non-null object then use it otherwise just use the new instance.
     console.log(result && typeof result === 'object' ? result : newInstance);

     _76, urutan log akan berurutan

     function Person(name) {
       this.name = name;
       this.age = 21;
     }
     var object = new Person("Sudheer");

     _67

     dan outputnya adalah,

     function Person(name) {
       this.name = name;
       this.age = 21;
     }
     var object = new Person("Sudheer");

     _68

386. Bagaimana Anda menerapkan batas waktu nol di browser modern

     Anda tidak dapat menggunakan setTimeout(fn, 0) untuk segera mengeksekusi kode karena penundaan minimum lebih dari 0 md. But you can use window. postMessage() untuk mencapai perilaku ini

387. Apa tugas dalam loop acara

     Tugas adalah kode/program javascript apa pun yang dijadwalkan untuk dijalankan oleh mekanisme standar seperti awalnya mulai menjalankan program, menjalankan panggilan balik acara, atau interval atau batas waktu yang dipecat. Semua tugas ini dijadwalkan pada antrian tugas. Di bawah ini adalah daftar kasus penggunaan untuk menambahkan tugas ke antrean tugas,

     1. Saat program javascript baru dijalankan langsung dari konsol atau dijalankan oleh elemen

        class Person {
          constructor(name) {
            this.name = name;
          }
        }
        
        var object = new Person("Sudheer");

        29, tugas akan ditambahkan ke antrian tugas
     2. Saat suatu peristiwa diaktifkan, panggilan balik peristiwa ditambahkan ke antrean tugas
     3. Saat setTimeout atau setInterval tercapai, panggilan balik terkait ditambahkan ke antrean tugas

388. Apa itu tugas mikro

     Microtask adalah kode javascript yang perlu dieksekusi segera setelah tugas/microtask yang sedang dieksekusi selesai. Mereka agak memblokir di alam. Saya. e, Utas utama akan diblokir sampai antrian microtask kosong. Sumber utama microtasks adalah Promise. putuskan, Janji. tolak, MutationObservers, IntersectionObservers dll

     Catatan. All of these microtasks are processed in the same turn of the event loop.

389. Apa itu loop acara yang berbeda

390. Apa tujuan dari queueMicrotask

391. Bagaimana Anda menggunakan pustaka javascript dalam file TypeScript

     Diketahui bahwa tidak semua pustaka atau kerangka kerja JavaScript memiliki file deklarasi TypeScript. Tetapi jika Anda masih ingin menggunakan pustaka atau kerangka kerja di file TypeScript kami tanpa mendapatkan kesalahan kompilasi, satu-satunya solusi adalah kata kunci

     class Person {
       constructor(name) {
         this.name = name;
       }
     }
     
     var object = new Person("Sudheer");

     30 bersama dengan deklarasi variabel. Misalnya, bayangkan Anda memiliki pustaka bernama

     class Person {
       constructor(name) {
         this.name = name;
       }
     }
     
     var object = new Person("Sudheer");

     31 yang tidak memiliki deklarasi TypeScript dan memiliki namespace bernama

     class Person {
       constructor(name) {
         this.name = name;
       }
     }
     
     var object = new Person("Sudheer");

     31 di namespace global. Anda dapat menggunakan perpustakaan ini dalam kode TypeScript seperti di bawah ini,

     function Person(name) {
       this.name = name;
       this.age = 21;
     }
     var object = new Person("Sudheer");

     _69

     Saat runtime, TypeScript akan memberikan tipe ke variabel

     class Person {
       constructor(name) {
         this.name = name;
       }
     }
     
     var object = new Person("Sudheer");

     31 sebagai tipe

     class Person {
       constructor(name) {
         this.name = name;
       }
     }
     
     var object = new Person("Sudheer");

     34. Alternatif lain tanpa menggunakan kata kunci menyatakan di bawah ini

     function Person(name) {
       this.name = name;
       this.age = 21;
     }
     var object = new Person("Sudheer");

     _70

392. Apa perbedaan antara janji dan yang bisa diamati

     Some of the major difference in a tabular form

     PromisesObservablesEmits hanya satu nilai pada satu waktuEmits beberapa nilai selama periode waktu (aliran nilai mulai dari 0 hingga beberapa)Bersemangat di alam;

393. Apa itu tumpukan

     Heap(Atau tumpukan memori) adalah lokasi memori tempat objek disimpan saat kita mendefinisikan variabel. Saya. e, This is the place where all the memory allocations and de-allocation take place. Heap dan call-stack adalah dua kontainer runtime JS. Setiap kali runtime menemukan variabel dan deklarasi fungsi dalam kode, ia menyimpannya di Heap

     

394. Apa itu meja acara

     Tabel Peristiwa adalah struktur data yang menyimpan dan melacak semua peristiwa yang akan dieksekusi secara asinkron seperti setelah beberapa interval waktu atau setelah penyelesaian beberapa permintaan API. Saya. e Setiap kali Anda memanggil fungsi setTimeout atau menjalankan operasi async, fungsi tersebut akan ditambahkan ke Tabel Acara. Itu tidak menjalankan fungsi sendiri. Tujuan utama dari tabel acara adalah untuk melacak acara dan mengirimkannya ke Antrean Acara seperti yang ditunjukkan pada diagram di bawah ini

     

395. Apa itu antrian microTask

     Antrean Microtask adalah antrean baru tempat semua tugas yang diprakarsai oleh objek janji diproses sebelum antrean panggilan balik. Antrean microtasks diproses sebelum pekerjaan rendering dan pengecatan berikutnya. Tetapi jika microtasks ini berjalan dalam waktu lama maka akan menyebabkan degradasi visual

396. Apa perbedaan antara shim dan polyfill

     Shim adalah perpustakaan yang membawa API baru ke lingkungan yang lebih lama, hanya menggunakan alat dari lingkungan itu. Itu tidak selalu terbatas pada aplikasi web. Misalnya, es5-shim. js digunakan untuk meniru fitur ES5 di browser lama (terutama sebelum IE9). Whereas polyfill is a piece of code (or plugin) that provides the technology that you, the developer, expect the browser to provide natively. Dalam kalimat sederhana, Polyfill adalah shim untuk API browser

397. Bagaimana Anda mendeteksi tipe nilai primitif atau non primitif

     Dalam JavaScript, tipe primitif termasuk boolean, string, angka, BigInt, null, Simbol, dan tidak terdefinisi. Sedangkan tipe non-primitif termasuk Objek. Tetapi Anda dapat dengan mudah mengidentifikasinya dengan fungsi di bawah ini,

     function Person(name) {
       this.name = name;
       this.age = 21;
     }
     var object = new Person("Sudheer");

     _71

     Jika nilainya adalah tipe data primitif, konstruktor Objek membuat objek pembungkus baru untuk nilainya. Tetapi jika nilainya adalah tipe data non-primitif (objek), konstruktor Objek akan memberikan objek yang sama

398. Apa itu babel

     Babel adalah transpiler JavaScript untuk mengonversi kode ECMAScript 2015+ menjadi versi JavaScript yang kompatibel mundur di browser atau lingkungan saat ini dan yang lebih lama. Beberapa fitur utama tercantum di bawah ini,

     1. Mengubah sintaks
     2. Fitur Polyfill yang tidak ada di lingkungan target Anda (menggunakan @babel/polyfill)
     3. Transformasi kode sumber (atau codemods)

399. Apakah Node. js sepenuhnya berulir tunggal

     Node adalah utas tunggal, tetapi beberapa fungsi termasuk dalam Node. js standard library(e. g, fungsi modul fs) bukan utas tunggal. Saya. e, Logika mereka berjalan di luar Node. js single thread untuk meningkatkan kecepatan dan performa program

400. Apa kasus penggunaan umum yang dapat diamati

     Beberapa kasus penggunaan paling umum yang dapat diamati adalah soket web dengan pemberitahuan push, perubahan input pengguna, interval berulang, dll.

401. Apa itu RxJS

     RxJS (Ekstensi Reaktif untuk JavaScript) adalah pustaka untuk mengimplementasikan pemrograman reaktif menggunakan objek yang dapat diamati yang membuatnya lebih mudah untuk menyusun kode berbasis asinkron atau panggilan balik. Ini juga menyediakan fungsi utilitas untuk membuat dan bekerja dengan yang dapat diamati

402. Apa perbedaan antara konstruktor Fungsi dan deklarasi fungsi

     Fungsi yang dibuat dengan

     class Person {
       constructor(name) {
         this.name = name;
       }
     }
     
     var object = new Person("Sudheer");

     _35 tidak membuat penutupan untuk konteks pembuatannya tetapi selalu dibuat dalam lingkup global. Saya. e, fungsi dapat mengakses variabel lokalnya sendiri dan variabel lingkup global saja. Sedangkan deklarasi fungsi juga dapat mengakses variabel fungsi luar (penutupan).

     Mari kita lihat perbedaan ini dengan sebuah contoh,

     Pembuat Fungsi

     function Person(name) {
       this.name = name;
       this.age = 21;
     }
     var object = new Person("Sudheer");

     _72

     Deklarasi fungsi

     function Person(name) {
       this.name = name;
       this.age = 21;
     }
     var object = new Person("Sudheer");

     73

403. Apa itu kondisi hubung singkat

     Kondisi hubung singkat dimaksudkan untuk cara singkat menulis pernyataan if sederhana. Mari kita tunjukkan skenario menggunakan contoh. Jika Anda ingin masuk ke portal dengan kondisi autentikasi, ekspresinya akan seperti di bawah ini,

     function Person(name) {
       this.name = name;
       this.age = 21;
     }
     var object = new Person("Sudheer");

     _74

     Karena operator logis javascript dievaluasi dari kiri ke kanan, ekspresi di atas dapat disederhanakan menggunakan && operator logis

     function Person(name) {
       this.name = name;
       this.age = 21;
     }
     var object = new Person("Sudheer");

     _75

404. Apa cara termudah untuk mengubah ukuran array

     Properti length dari array berguna untuk mengubah ukuran atau mengosongkan array dengan cepat. Mari terapkan properti length pada array angka untuk mengubah ukuran jumlah elemen dari 5 menjadi 2,

     function Person(name) {
       this.name = name;
       this.age = 21;
     }
     var object = new Person("Sudheer");

     _76

     dan array juga bisa dikosongkan

     function Person(name) {
       this.name = name;
       this.age = 21;
     }
     var object = new Person("Sudheer");

     _77

405. Apa yang bisa diamati

     Observable pada dasarnya adalah fungsi yang dapat mengembalikan aliran nilai baik secara sinkron atau asinkron ke pengamat dari waktu ke waktu. Konsumen bisa mendapatkan nilai dengan memanggil metode

     class Person {
       constructor(name) {
         this.name = name;
       }
     }
     
     var object = new Person("Sudheer");

     36. Mari kita lihat contoh sederhana dari Observable

     function Person(name) {
       this.name = name;
       this.age = 21;
     }
     var object = new Person("Sudheer");

     _78
     

     Note. Observable belum menjadi bagian dari bahasa JavaScript tetapi diusulkan untuk ditambahkan ke bahasa tersebut

406. Apa perbedaan antara deklarasi fungsi dan kelas

     Perbedaan utama antara deklarasi fungsi dan deklarasi kelas adalah

     class Person {
       constructor(name) {
         this.name = name;
       }
     }
     
     var object = new Person("Sudheer");

     37. Deklarasi fungsi diangkat tetapi bukan deklarasi kelas

     Kelas

     function Person(name) {
       this.name = name;
       this.age = 21;
     }
     var object = new Person("Sudheer");

     _79

     Fungsi Konstruktor

     function Person(name) {
       this.name = name;
       this.age = 21;
     }
     var object = new Person("Sudheer");

     _80

407. Apa itu fungsi async

     Fungsi asinkron adalah fungsi yang dideklarasikan dengan kata kunci

     class Person {
       constructor(name) {
         this.name = name;
       }
     }
     
     var object = new Person("Sudheer");

     38 yang memungkinkan perilaku asinkron berbasis janji untuk ditulis dalam gaya yang lebih bersih dengan menghindari rantai janji. Fungsi ini dapat berisi nol atau lebih

     class Person {
       constructor(name) {
         this.name = name;
       }
     }
     
     var object = new Person("Sudheer");

     39 ekspresi

     Mari kita ambil contoh fungsi async di bawah ini,

     function Person(name) {
       this.name = name;
       this.age = 21;
     }
     var object = new Person("Sudheer");

     _81

     Ini pada dasarnya adalah gula sintaksis atas janji dan generator ES2015

408. Bagaimana Anda mencegah janji menelan kesalahan

     Saat menggunakan kode asinkron, janji ES6 JavaScript dapat membuat hidup Anda jauh lebih mudah tanpa piramida panggilan balik dan penanganan kesalahan di setiap baris kedua. Tapi Janji memiliki beberapa jebakan dan yang terbesar adalah menelan kesalahan secara default

     Katakanlah Anda berharap mencetak kesalahan ke konsol untuk semua kasus di bawah ini,

     function Person(name) {
       this.name = name;
       this.age = 21;
     }
     var object = new Person("Sudheer");

     82

     Tetapi ada banyak lingkungan JavaScript modern yang tidak mencetak kesalahan apa pun. Anda dapat memperbaiki masalah ini dengan berbagai cara,

     1. Tambahkan blok tangkap di akhir setiap rantai. Anda dapat menambahkan blok tangkap di akhir setiap rantai janji Anda

        function Person(name) {
          this.name = name;
          this.age = 21;
        }
        var object = new Person("Sudheer");

        _83

        Tetapi cukup sulit untuk mengetik untuk setiap rantai janji dan juga verbose

     2. Tambahkan metode selesai. Anda dapat mengganti solusi pertama kemudian dan menangkap blok dengan metode selesai

        function Person(name) {
          this.name = name;
          this.age = 21;
        }
        var object = new Person("Sudheer");

        _84

        Katakanlah Anda ingin mengambil data menggunakan HTTP dan kemudian melakukan pemrosesan pada data yang dihasilkan secara asinkron. Anda dapat menulis blok

        // Create a new instance using function prototype.
        var newInstance = Object.create(func.prototype)
        
        // Call the function
        var result = func.call(newInstance, x, y, z),
        
        // If the result is a non-null object then use it otherwise just use the new instance.
        console.log(result && typeof result === 'object' ? result : newInstance);

        _31 seperti di bawah ini,

        function Person(name) {
          this.name = name;
          this.age = 21;
        }
        var object = new Person("Sudheer");

        _85

        Di masa mendatang, jika API perpustakaan pemrosesan berubah menjadi sinkron maka Anda dapat menghapus

        // Create a new instance using function prototype.
        var newInstance = Object.create(func.prototype)
        
        // Call the function
        var result = func.call(newInstance, x, y, z),
        
        // If the result is a non-null object then use it otherwise just use the new instance.
        console.log(result && typeof result === 'object' ? result : newInstance);

        31 blok seperti di bawah ini,

        function Person(name) {
          this.name = name;
          this.age = 21;
        }
        var object = new Person("Sudheer");

        _86

        dan kemudian Anda lupa menambahkan

        // Create a new instance using function prototype.
        var newInstance = Object.create(func.prototype)
        
        // Call the function
        var result = func.call(newInstance, x, y, z),
        
        // If the result is a non-null object then use it otherwise just use the new instance.
        console.log(result && typeof result === 'object' ? result : newInstance);

        _31 blok ke

        class Person {
          constructor(name) {
            this.name = name;
          }
        }
        
        var object = new Person("Sudheer");

        43 blok menyebabkan kesalahan diam

     3. Perpanjang Janji ES6 oleh Bluebird. Bluebird memperluas ES6 Promises API untuk menghindari masalah di solusi kedua. Pustaka ini memiliki penangan onRejection "default" yang akan mencetak semua kesalahan dari Janji yang ditolak ke stderr. After installation, you can process unhandled rejections

        function Person(name) {
          this.name = name;
          this.age = 21;
        }
        var object = new Person("Sudheer");

        _87

        dan buang penolakan, tangani saja dengan tangkapan kosong

        function Person(name) {
          this.name = name;
          this.age = 21;
        }
        var object = new Person("Sudheer");

        _88

409. Apa itu den

     Deno is a simple, modern and secure runtime for JavaScript and TypeScript that uses V8 JavaScript engine and the Rust programming language

410. Bagaimana Anda membuat objek dapat diubah dalam javascript

     Secara default, objek biasa tidak dapat diubah. Tapi Anda bisa membuat objek iterable dengan mendefinisikan properti

     class Person {
       constructor(name) {
         this.name = name;
       }
     }
     
     var object = new Person("Sudheer");

     44 di atasnya

     Let's demonstrate this with an example,

     function Person(name) {
       this.name = name;
       this.age = 21;
     }
     var object = new Person("Sudheer");

     89

     The above process can be simplified using a generator function,

     function Person(name) {
       this.name = name;
       this.age = 21;
     }
     var object = new Person("Sudheer");

     _90

411. Apa itu Panggilan Ekor yang Tepat

     First, we should know about tail call before talking about "Proper Tail Call". Tail call adalah subrutin atau pemanggilan fungsi yang dilakukan sebagai tindakan terakhir dari pemanggilan fungsi. Sedangkan Proper tail call (PTC) adalah teknik di mana program atau kode tidak akan membuat frame stack tambahan untuk rekursi ketika pemanggilan fungsi adalah panggilan ekor

     For example, the below classic or head recursion of factorial function relies on stack for each step. Setiap langkah perlu diproses hingga

     class Person {
       constructor(name) {
         this.name = name;
       }
     }
     
     var object = new Person("Sudheer");

     _45

     function Person(name) {
       this.name = name;
       this.age = 21;
     }
     var object = new Person("Sudheer");

     91

     But if you use Tail recursion functions, they keep passing all the necessary data it needs down the recursion without relying on the stack

     function Person(name) {
       this.name = name;
       this.age = 21;
     }
     var object = new Person("Sudheer");

     _92

     Pola di atas mengembalikan output yang sama dengan yang pertama. But the accumulator keeps track of total as an argument without using stack memory on recursive calls

412. Bagaimana Anda memeriksa suatu objek adalah janji atau tidak

     Jika Anda tidak tahu apakah suatu nilai adalah janji atau bukan, bungkus nilai sebagai

     class Person {
       constructor(name) {
         this.name = name;
       }
     }
     
     var object = new Person("Sudheer");

     46 yang mengembalikan janji

     function Person(name) {
       this.name = name;
       this.age = 21;
     }
     var object = new Person("Sudheer");

     _93

     Another way is to check for

     function func() {};
     
     new func(x, y, z);

     71 handler type

     function Person(name) {
       this.name = name;
       this.age = 21;
     }
     var object = new Person("Sudheer");

     _94

413. Cara mendeteksi jika suatu fungsi disebut sebagai konstruktor

     You can use

     class Person {
       constructor(name) {
         this.name = name;
       }
     }
     
     var object = new Person("Sudheer");

     48 pseudo-property to detect whether a function was called as a constructor(using the new operator) or as a regular function call
     1. If a constructor or function invoked using the new operator, new. target mengembalikan referensi ke konstruktor atau fungsi
     2. For function calls, new. target is undefined

     function Person(name) {
       this.name = name;
       this.age = 21;
     }
     var object = new Person("Sudheer");

     _95

414. What are the differences between arguments object and rest parameter

     Ada tiga perbedaan utama antara objek argumen dan parameter lainnya

     1. Objek argumen adalah seperti array tetapi bukan array. Whereas the rest parameters are array instances
     2. The arguments object does not support methods such as sort, map, forEach, or pop. Padahal metode tersebut dapat digunakan pada parameter rest
     3. The rest parameters are only the ones that haven’t been given a separate name, while the arguments object contains all arguments passed to the function

415. Apa perbedaan antara operator spread dan parameter istirahat

     Rest parameter collects all remaining elements into an array. Sedangkan operator Spread memungkinkan iterables (array / objek / string) untuk diperluas menjadi argumen / elemen tunggal. i. e, parameter Istirahat berlawanan dengan operator spread

416. What are the different kinds of generators

     There are five kinds of generators,

     1. Generator function declaration

        function Person(name) {
          this.name = name;
          this.age = 21;
        }
        var object = new Person("Sudheer");

        _96

     2. Ekspresi fungsi generator

        function Person(name) {
          this.name = name;
          this.age = 21;
        }
        var object = new Person("Sudheer");

        _97

     3. Definisi metode generator dalam literal objek

        function Person(name) {
          this.name = name;
          this.age = 21;
        }
        var object = new Person("Sudheer");

        _98

     4. Definisi metode generator di kelas

        function Person(name) {
          this.name = name;
          this.age = 21;
        }
        var object = new Person("Sudheer");

        99

     5. Generator as a computed property

        function Person() {}
        Person.prototype.name = "Sudheer";
        var object = new Person();

        00

417. Apa itu iterables bawaan

     Di bawah ini adalah daftar iterable bawaan dalam javascript,

     1. Arrays and TypedArrays
     2. String. Iterate over each character or Unicode code-points
     3. Maps. ulangi pasangan kunci-nilainya
     4. Sets. iterates over their elements
     5. argumen. Variabel khusus seperti array dalam fungsi
     6. DOM collection such as NodeList

418. Apa perbedaan antara untuk. of and for. dalam pernyataan

     Keduanya untuk. in and for. pernyataan iterate atas struktur data js. Satu-satunya perbedaan adalah pada apa yang mereka iterasi

     1. for. di mengulangi semua kunci properti yang dapat dihitung dari suatu objek
     2. untuk. of iterates over the values of an iterable object

     Let's explain this difference with an example,

     function Person() {}
     Person.prototype.name = "Sudheer";
     var object = new Person();

     01

     Since for. dalam loop mengulangi kunci objek, loop pertama mencatat 0, 1, 2 dan newProp sambil mengulangi objek array. The for. of loop iterates over the values of a arr data structure and logs a, b, c in the console

419. How do you define instance and non-instance properties

     The Instance properties must be defined inside of class methods. For example, name and age properties defined inside constructor as below,

     function Person() {}
     Person.prototype.name = "Sudheer";
     var object = new Person();

     02

     Tetapi properti data Statis(kelas) dan prototipe harus didefinisikan di luar deklarasi ClassBody. Let's assign the age value for Person class as below,

     function Person() {}
     Person.prototype.name = "Sudheer";
     var object = new Person();

     _03

420. What is the difference between isNaN and Number. isNaN?

     1. isNaN. The global function

        class Person {
          constructor(name) {
            this.name = name;
          }
        }
        
        var object = new Person("Sudheer");

        49 converts the argument to a Number and returns true if the resulting value is NaN
     2. Nomor. isNaN. This method does not convert the argument. But it returns true when the type is a Number and value is NaN

     Let's see the difference with an example,

     function Person() {}
     Person.prototype.name = "Sudheer";
     var object = new Person();

     _04

421. How to invoke an IIFE without any extra brackets?

     Ekspresi Fungsi Segera Dipanggil (IIFE) membutuhkan sepasang tanda kurung untuk membungkus fungsi yang berisi kumpulan pernyataan

     function Person() {}
     Person.prototype.name = "Sudheer";
     var object = new Person();

     _05

     Karena operator IIFE dan void membuang hasil ekspresi, Anda dapat menghindari tanda kurung ekstra menggunakan

     class Person {
       constructor(name) {
         this.name = name;
       }
     }
     
     var object = new Person("Sudheer");

     50 untuk IIFE seperti di bawah ini,

     function Person() {}
     Person.prototype.name = "Sudheer";
     var object = new Person();

     _06

422. Is that possible to use expressions in switch cases?

     You might have seen expressions used in switch condition but it is also possible to use for switch cases by assigning true value for the switch condition. Let's see the weather condition based on temparature as an example,

     function Person() {}
     Person.prototype.name = "Sudheer";
     var object = new Person();

     _07

423. What is the easiest way to ignore promise errors?

     Cara termudah dan teraman untuk mengabaikan kesalahan janji adalah membatalkan kesalahan itu. Pendekatan ini juga ramah ESLint

     function Person() {}
     Person.prototype.name = "Sudheer";
     var object = new Person();

     08

424. How do style the console output using CSS?

     Anda dapat menambahkan gaya CSS ke keluaran konsol menggunakan penentu konten format CSS %c. The console string message can be appended after the specifier and CSS style in another argument. Mari cetak teks warna merah menggunakan konsol. log dan penentu CSS seperti di bawah ini,

     function Person() {}
     Person.prototype.name = "Sudheer";
     var object = new Person();

     _09

     Dimungkinkan juga untuk menambahkan lebih banyak gaya untuk konten. For example, the font-size can be modified for the above text

     function Person() {}
     Person.prototype.name = "Sudheer";
     var object = new Person();

     _10

425. What is nullish coalescing operator (??)?

     It is a logical operator that returns its right-hand side operand when its left-hand side operand is null or undefined, and otherwise returns its left-hand side operand. This can be contrasted with the logical OR (. ) operator, which returns the right-hand side operand if the left operand is any falsy value, not only null or undefined

     function Person() {}
     Person.prototype.name = "Sudheer";
     var object = new Person();

     _11

426. How do you group and nest console output?

     The

     class Person {
       constructor(name) {
         this.name = name;
       }
     }
     
     var object = new Person("Sudheer");

     51 can be used to group related log messages to be able to easily read the logs and use console. groupEnd() untuk menutup grup. Along with this, you can also nest groups which allows to output message in hierarchical manner

     Misalnya, jika Anda mencatat detail pengguna

     function Person() {}
     Person.prototype.name = "Sudheer";
     var object = new Person();

     _12

     Anda juga dapat menggunakan

     class Person {
       constructor(name) {
         this.name = name;
       }
     }
     
     var object = new Person("Sudheer");

     52 alih-alih

     class Person {
       constructor(name) {
         this.name = name;
       }
     }
     
     var object = new Person("Sudheer");

     51 jika Anda ingin grup diciutkan secara default

427. What is the difference between dense and sparse arrays?

     An array contains items at each index starting from first(0) to last(array. length - 1) is called as Dense array. Sedangkan jika setidaknya satu item hilang pada indeks mana pun, array disebut jarang

     Mari kita lihat dua jenis array di bawah ini,

     function Person() {}
     Person.prototype.name = "Sudheer";
     var object = new Person();

     _13

428. What are the different ways to create sparse arrays?

     There are 4 different ways to create sparse arrays in JavaScript

     1. Array literal. Hilangkan nilai saat menggunakan array literal

        function Person() {}
        Person.prototype.name = "Sudheer";
        var object = new Person();

        _14

     2. Array() konstruktor. Memanggil Array(panjang) atau Array(panjang) baru

        function Person() {}
        Person.prototype.name = "Sudheer";
        var object = new Person();

        _15

     3. Hapus operator. Menggunakan operator delete array[index] pada array

        function Person() {}
        Person.prototype.name = "Sudheer";
        var object = new Person();

        _16

     4. Tingkatkan properti panjang. Increasing length property of an array

        function Person() {}
        Person.prototype.name = "Sudheer";
        var object = new Person();

        _17

429. Apa perbedaan antara setTimeout, setImmediate, dan proses. nextTick?

     1. Tetapkan Batas Waktu. setTimeout() adalah menjadwalkan eksekusi panggilan balik satu kali setelah penundaan milidetik
     2. Tetapkan Segera. Fungsi setImmediate digunakan untuk menjalankan fungsi tepat setelah perulangan peristiwa saat ini selesai
     3. Proses BerikutnyaCentang. If process. nextTick() dipanggil dalam fase tertentu, semua panggilan balik diteruskan ke proses. nextTick() akan diselesaikan sebelum event loop berlanjut. Ini akan memblokir loop acara dan membuat I/O Starvation jika proses. nextTick() disebut secara rekursif

430. Bagaimana Anda membalikkan array tanpa mengubah array asli?

     Metode

     class Person {
       constructor(name) {
         this.name = name;
       }
     }
     
     var object = new Person("Sudheer");

     _54 membalikkan urutan elemen dalam array tetapi mengubah array asli. Mari kita ambil contoh sederhana untuk mendemonstrasikan kasus ini,

     function Person() {}
     Person.prototype.name = "Sudheer";
     var object = new Person();

     _18

     Ada beberapa solusi yang tidak akan mengubah array asli. Mari lihat

     1. Menggunakan metode slice dan reverse. Dalam hal ini, aktifkan saja metode

        class Person {
          constructor(name) {
            this.name = name;
          }
        }
        
        var object = new Person("Sudheer");

        _55 pada array untuk membuat salinan dangkal diikuti dengan panggilan metode

        class Person {
          constructor(name) {
            this.name = name;
          }
        }
        
        var object = new Person("Sudheer");

        54 pada salinan

        function Person() {}
        Person.prototype.name = "Sudheer";
        var object = new Person();

        _19

     2. Menggunakan metode spread dan reverse. Dalam hal ini, mari gunakan sintaks spread (. ) untuk membuat salinan array diikuti dengan panggilan metode

        class Person {
          constructor(name) {
            this.name = name;
          }
        }
        
        var object = new Person("Sudheer");

        54 pada salinan

        function Person() {}
        Person.prototype.name = "Sudheer";
        var object = new Person();

        _20

     3. Menggunakan metode pengurangan dan penyebaran. Di sini jalankan fungsi peredam pada elemen array dan tambahkan array yang terakumulasi di sisi kanan menggunakan sintaks spread

        function Person() {}
        Person.prototype.name = "Sudheer";
        var object = new Person();

        _21

     4. Menggunakan metode reduceRight dan spread. Here execute a right reducer function(i. e. arah berlawanan dari metode pengurangan) pada elemen array dan tambahkan array terakumulasi di sisi kiri menggunakan sintaks spread

        function Person() {}
        Person.prototype.name = "Sudheer";
        var object = new Person();

        _22

     5. Menggunakan metode reduceRight dan push. Di sini jalankan fungsi peredam kanan (i. e. arah berlawanan dari metode pengurangan) pada elemen array dan Dorong nilai iterasi ke akumulator

        function Person() {}
        Person.prototype.name = "Sudheer";
        var object = new Person();

        23

431. Bagaimana Anda membuat elemen HTML khusus?

     Pembuatan elemen HTML kustom melibatkan dua langkah utama,

     1. Tentukan elemen HTML khusus Anda. Pertama, Anda perlu mendefinisikan beberapa kelas khusus dengan memperluas kelas HTMLElement. Setelah itu tentukan properti komponen Anda (gaya, teks dll) menggunakan metode

        class Person {
          constructor(name) {
            this.name = name;
          }
        }
        
        var object = new Person("Sudheer");

        58. Catatan. Browser memaparkan fungsi yang disebut

        class Person {
          constructor(name) {
            this.name = name;
          }
        }
        
        var object = new Person("Sudheer");

        _59 untuk menggunakan kembali elemen tersebut

        function Person() {}
        Person.prototype.name = "Sudheer";
        var object = new Person();

        _24

     2. Use custome element just like other HTML element. Nyatakan elemen khusus Anda sebagai tag HTML

     function Person() {}
     Person.prototype.name = "Sudheer";
     var object = new Person();

     25

432. Apa itu konteks eksekusi global?

     The global execution context is the default or first execution context that is created by the JavaScript engine before any code is executed(i. e, saat file pertama kali dimuat di browser). Semua kode global yang tidak ada di dalam fungsi atau objek akan dieksekusi di dalam konteks eksekusi global ini. Karena mesin JS adalah utas tunggal, hanya akan ada satu lingkungan global dan hanya akan ada satu konteks eksekusi global

     Misalnya, kode di bawah selain kode di dalam fungsi atau objek apa pun dijalankan di dalam konteks eksekusi global

     function Person() {}
     Person.prototype.name = "Sudheer";
     var object = new Person();

     _26

433. Apa itu konteks eksekusi fungsi?

     Whenever a function is invoked, the JavaScript engine creates a different type of Execution Context known as a Function Execution Context (FEC) within the Global Execution Context (GEC) to evaluate and execute the code within that function

434. Apa itu debouncing?

     Debouncing is a programming pattern that allows delaying execution of some piece of code until a specified time to avoid unnecessary CPU cycles, API calls and improve performance. Fungsi debounce memastikan bahwa kode Anda hanya dipicu sekali per input pengguna. Kasus penggunaan yang umum adalah saran kotak Pencarian, penyimpanan otomatis bidang teks, dan menghilangkan klik tombol dua kali

     Katakanlah Anda ingin menampilkan saran untuk kueri penelusuran, tetapi hanya setelah pengunjung selesai mengetiknya. Jadi di sini Anda menulis fungsi debounce di mana pengguna terus menulis karakter dalam 500 md kemudian pengatur waktu sebelumnya dihapus menggunakan

     class Person {
       constructor(name) {
         this.name = name;
       }
     }
     
     var object = new Person("Sudheer");

     60 dan menjadwal ulang permintaan panggilan/DB API untuk waktu baru—300 md di masa mendatang

     function Person() {}
     Person.prototype.name = "Sudheer";
     var object = new Person();

     _27

     Fungsi debounce() dapat digunakan pada peristiwa input, tombol, dan jendela

     Memasukkan

     function Person() {}
     Person.prototype.name = "Sudheer";
     var object = new Person();

     _28

     Tombol

     function Person() {}
     Person.prototype.name = "Sudheer";
     var object = new Person();

     _29

     acara Windows

     function Person() {}
     Person.prototype.name = "Sudheer";
     var object = new Person();

     _30

435. Apa itu throttling?

     Throttling adalah teknik yang digunakan untuk membatasi eksekusi fungsi event handler, bahkan saat event ini terpicu terus menerus karena tindakan pengguna. Kasus penggunaan yang umum adalah pengubahan ukuran browser, pengguliran jendela, dll

     Contoh di bawah membuat fungsi throttle untuk mengurangi jumlah kejadian untuk setiap perubahan piksel dan memicu kejadian gulir untuk setiap 100 md kecuali untuk kejadian pertama

     function Person() {}
     Person.prototype.name = "Sudheer";
     var object = new Person();

     _31

436. Apa itu rangkaian opsional?

     Menurut dokumen resmi MDN, operator rangkaian opsional (?. ) memungkinkan membaca nilai properti yang terletak jauh di dalam rantai objek yang terhubung tanpa harus secara tegas memvalidasi bahwa setiap referensi dalam rantai itu valid

     Itu?. operatornya seperti. operator rantai, kecuali bahwa alih-alih menyebabkan kesalahan jika referensi adalah nullish (nol atau tidak terdefinisi), ekspresi hubungan pendek dengan nilai kembalian tidak terdefinisi. Saat digunakan dengan pemanggilan fungsi, ia mengembalikan undefined jika fungsi yang diberikan tidak ada

     function Person() {}
     Person.prototype.name = "Sudheer";
     var object = new Person();

     _32

437. Apa itu catatan lingkungan?

     Menurut spesifikasi ECMAScript 262 (9. 1)

     adalah tipe spesifikasi yang digunakan untuk menentukan asosiasi Pengidentifikasi ke variabel dan fungsi tertentu, berdasarkan struktur bersarang leksikal kode ECMAScript

     Biasanya Catatan Lingkungan dikaitkan dengan beberapa struktur sintaksis tertentu dari kode ECMAScript seperti FunctionDeclaration, BlockStatement, atau klausa Catch dari TryStatement

     Setiap kali kode tersebut dievaluasi, Catatan Lingkungan baru dibuat untuk merekam pengikatan pengidentifikasi yang dibuat oleh kode tersebut

438. Bagaimana cara memverifikasi jika suatu variabel adalah array?

     Dimungkinkan untuk memeriksa apakah suatu variabel adalah instance array menggunakan 3 cara berbeda,

     1. Himpunan. metode isArray()

        Fungsi utilitas

        class Person {
          constructor(name) {
            this.name = name;
          }
        }
        
        var object = new Person("Sudheer");

        _61 digunakan untuk menentukan apakah nilai adalah array atau bukan. Fungsi ini mengembalikan nilai boolean yang benar jika variabelnya adalah array dan nilai yang salah jika bukan

        function Person() {}
        Person.prototype.name = "Sudheer";
        var object = new Person();

        _33

     2. operator instanceof

        Operator instanceof digunakan untuk memeriksa jenis array pada saat dijalankan. Mengembalikan nilai true jika tipe variabel adalah Array other false untuk tipe lainnya

        function Person() {}
        Person.prototype.name = "Sudheer";
        var object = new Person();

        _34

     3. Memeriksa tipe konstruktor

        Properti konstruktor dari variabel tersebut digunakan untuk menentukan apakah variabel tersebut bertipe Array atau tidak

        function Person() {}
        Person.prototype.name = "Sudheer";
        var object = new Person();

        _35

439. Apa itu pass by value dan pass by reference?

     Pass-by-value membuat ruang baru di memori dan membuat salinan dari sebuah nilai. Primitif seperti string, angka, boolean dll sebenarnya akan membuat salinan baru. Oleh karena itu, memperbarui satu nilai tidak memengaruhi nilai lainnya. Saya. e, Nilai-nilai tidak tergantung satu sama lain

     function Person() {}
     Person.prototype.name = "Sudheer";
     var object = new Person();

     _36

     Dalam cuplikan kode di atas, nilai

     class Person {
       constructor(name) {
         this.name = name;
       }
     }
     
     var object = new Person("Sudheer");

     _62 ditugaskan ke

     // Create a new instance using function prototype.
     var newInstance = Object.create(func.prototype)
     
     // Call the function
     var result = func.call(newInstance, x, y, z),
     
     // If the result is a non-null object then use it otherwise just use the new instance.
     console.log(result && typeof result === 'object' ? result : newInstance);

     18 dan variabel

     // Create a new instance using function prototype.
     var newInstance = Object.create(func.prototype)
     
     // Call the function
     var result = func.call(newInstance, x, y, z),
     
     // If the result is a non-null object then use it otherwise just use the new instance.
     console.log(result && typeof result === 'object' ? result : newInstance);

     18 telah bertambah. Karena ada ruang baru yang dibuat untuk variabel

     // Create a new instance using function prototype.
     var newInstance = Object.create(func.prototype)
     
     // Call the function
     var result = func.call(newInstance, x, y, z),
     
     // If the result is a non-null object then use it otherwise just use the new instance.
     console.log(result && typeof result === 'object' ? result : newInstance);

     18, setiap pembaruan pada variabel ini tidak memengaruhi variabel

     class Person {
       constructor(name) {
         this.name = name;
       }
     }
     
     var object = new Person("Sudheer");

     62

     Referensi lewat tidak membuat ruang baru di memori tetapi variabel baru mengadopsi alamat memori dari variabel awal. Non-primitif seperti objek, array, dan fungsi mendapatkan referensi dari variabel yang dapat diinisiasi. Saya. e, memperbarui satu nilai akan berdampak pada variabel lainnya

     function Person() {}
     Person.prototype.name = "Sudheer";
     var object = new Person();

     _37

     Dalam cuplikan kode di atas, memperbarui properti

     class Person {
       constructor(name) {
         this.name = name;
       }
     }
     
     var object = new Person("Sudheer");

     67 dari satu objek akan memengaruhi properti lainnya karena referensi yang sama

440. Apa perbedaan antara primitif dan non-primitif?

     Bahasa JavaScript memiliki primitif dan non-primitif tetapi ada beberapa perbedaan di antara keduanya seperti di bawah ini,

     Primitif Non-primitif Tipe ini telah ditentukan sebelumnya Dibuat oleh pengembang Ini tidak dapat diubah Dapat diubah Bandingkan dengan nilai Bandingkan dengan referensi Disimpan di StackStored di heapBerisi nilai tertentuDapat berisi NULL juga

441. Bagaimana Anda membuat metode bind Anda sendiri menggunakan metode call atau apply?

     Fungsi pengikatan khusus perlu dibuat pada prototipe Fungsi untuk menggunakannya sebagai fungsi bawaan lainnya. Fungsi kustom ini harus mengembalikan fungsi yang mirip dengan metode bind asli dan implementasi fungsi dalam perlu menggunakan panggilan metode apply

     Fungsi yang akan diikat menggunakan metode

     class Person {
       constructor(name) {
         this.name = name;
       }
     }
     
     var object = new Person("Sudheer");

     68 khusus bertindak sebagai fungsi terlampir (

     class Person {
       constructor(name) {
         this.name = name;
       }
     }
     
     var object = new Person("Sudheer");

     69) dan argumen sebagai objek untuk pemanggilan metode

     class Person {
       constructor(name) {
         this.name = name;
       }
     }
     
     var object = new Person("Sudheer");

     70

     function Person() {}
     Person.prototype.name = "Sudheer";
     var object = new Person();

     _38

442. Apa perbedaan antara fungsi murni dan tidak murni?