JS Tutorials
JS Introduction
JS Syntax
JS Comments
JS Variables
JS Operators
JS Data Types
JS Functions
JS Objects
JS Numbers
JS Arrays
JS Array Methods
JS Booleans
JS Events
JS Strings
JS Dates
JS Maths
JS Objects
Object Definition
Object Properties
Object Methods
Object Display
Object Prototypes
Object Iterables
Object Sets
Object Maps
Object References
JS Functions
Function Definition
Function Parameters
Function Invocation
Function Call
Function Apply
Function ClosuresJS Classes
Class Intro
Class Inhertitance
Class Static
JS Async
JS Callbacks
JS Aysnchronous
JS Prmosies
JS ASync/Await
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JavaScript Classes
ECMAScript 2015, also known as ES6, introduced JavaScript Classes.
JavaScript Classes are templates for JavaScript Objects.
JavaScript Class Syntax
Use the keyword class to create a class.
Always add a method named constructor():
Syntax
constructor() { ... }
}
Example
constructor(name, year) {
this.name = name;
this.year = year;
}
}
The example above creates a class named "Car".
The class has two initial properties: "name" and "year".
A JavaScript class is not an object.
It is a template for JavaScript objects.
Using a Class
When you have a class, you can use the class to create objects:
Example
let myCar2 = new Car("Audi", 2019);
The example above uses the Car class to create two Car objects.
The constructor method is called automatically when a new object is created.
The Constructor Method
The constructor method is a special method:
- It has to have the exact name "constructor"
- It is executed automatically when a new object is created
- It is used to initialize object properties
If you do not define a constructor method, JavaScript will add an empty constructor method.
Class Methods
Class methods are created with the same syntax as object methods.
Use the keyword class to create a class.
Always add a constructor() method.
Then add any number of methods.
Syntax
constructor() { ... }
method_1() { ... }
method_2() { ... }
method_3() { ... }
}
Create a Class method named "age", that returns the Car age:
Example
constructor(name, year) {
this.name = name;
this.year = year;
}
age() {
let date = new Date();
return date.getFullYear() - this.year;
}
}
let myCar = new Car("Ford", 2014);
document.getElementById("demo").innerHTML =
"My car is " + myCar.age() + " years old.";