In JavaScript, objects are king. If you understand objects, you understand JavaScript. Show
In JavaScript, almost "everything" is an object.
All JavaScript values, except primitives, are objects. JavaScript PrimitivesA primitive value is a value that has no properties or methods. 3.14 is a primitive value A primitive data type is data that has a primitive value. JavaScript defines 7 types of primitive data types: Examples
ImmutablePrimitive values are immutable (they are hardcoded and cannot be changed). if x = 3.14, you can change the value of x, but you cannot change the value of 3.14. ValueTypeComment"Hello"string"Hello" is always "Hello"3.14number3.14 is always 3.14truebooleantrue is always truefalsebooleanfalse is always falsenullnull (object)null is always nullundefinedundefinedundefined is always undefinedObjects are VariablesJavaScript variables can contain single values: JavaScript variables can also contain many values. Objects are variables too. But objects can contain many values. Object values are written as name : value pairs (name and value separated by a colon). Examplelet person = {firstName:"John", lastName:"Doe", age:50, eyeColor:"blue"}; Try it Yourself »A JavaScript object is a collection of named values It is a common practice to declare objects with the Exampleconst person = {firstName:"John", lastName:"Doe", age:50, eyeColor:"blue"}; Try it Yourself »Object PropertiesThe named values, in JavaScript objects, are called properties. PropertyValuefirstNameJohnlastNameDoeage50eyeColorblueObjects written as name value pairs are similar to:
Object MethodsMethods are actions that can be performed on objects. Object properties can be both primitive values, other objects, and functions. An object method is an object property containing a function definition. PropertyValuefirstNameJohnlastNameDoeage50eyeColorbluefullNamefunction() {return this.firstName + " " + this.lastName;}JavaScript objects are containers for named values, called properties and methods. You will learn more about methods in the next chapters. Creating a JavaScript ObjectWith JavaScript, you can define and create your own objects. There are different ways to create new objects:
Using an Object LiteralThis is the easiest way to create a JavaScript Object. Using an object literal, you both define and create an object in one statement. An object literal is a list of name:value pairs (like age:50) inside curly braces {}. The following example creates a new JavaScript object with four properties: Exampleconst person = {firstName:"John", lastName:"Doe", age:50, eyeColor:"blue"}; Try it Yourself »Spaces and line breaks are not important. An object definition can span multiple lines: Exampleconst person = { This example creates an empty JavaScript object, and then adds 4 properties: Exampleconst person = {}; Using the JavaScript Keyword newThe following example create a new JavaScript object using Exampleconst person = new Object(); The examples above do exactly the same. But there is no need to use For readability, simplicity and execution speed, use the object literal method. JavaScript Objects are MutableObjects are mutable: They are addressed by reference, not by value. If person is an object, the following statement will not create a copy of person: const x = person; // Will not create a copy of person. The object x is not a copy of person. It is person. Both x and person are the same object. Any changes to x will also change person, because x and person are the same object. Exampleconst person = { const x = person; Apa itu New di javascript?Sebuah fungsi yang dipanggil dengan diawali dengan perintah new pada Javascript dikenal dengan istilah constructor invocation. Setiap kali sebuah fungsi dipanggil dengan prefiks new , maka fungsi tersebut akan otomatis mengembalikan objek baru pada akhir fungsi, meskipun kita tidak memanggil perintah return .
Apa itu constructor di javascript?Constuctor. Adalah sebuah method/function yang di jalankan pertama kali ketika object di buat.
Apa itu method di javascript?Method — method ini digunakan untuk manipulasi array, seperti menambah item baru, menghapus, dan sebagainya.
Apa itu Instance di javascript?Instance merupakan objek yang memiliki properti dan method yang telah ditentukan oleh blueprint-nya (class), atau singkatnya adalah objek yang merupakan hasil realisasi dari sebuah blueprint. Sama seperti constructor function, untuk membuat instance dari class pada ES6 kita gunakan keyword new.
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