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JavaScript Class extends Keyword


Example

Create a class named "Model" which will inherit the methods from the "Car" class:

class Car {
  constructor(brand) {
    this.carname = brand;
  }
  present() {
    return 'I have a ' + this.carname;
  }
}

class Model extends Car {
  constructor(brand, mod) {
    super(brand);
    this.model = mod;
  }
  show() {
    return this.present() + ', it is a ' + this.model;
  }
}

mycar = new Model("Ford", "Mustang");
document.getElementById("demo").innerHTML = mycar.show();

Try it Yourself »


Definition and Usage

The extends keyword is used to create a child class of another class (parent).

The child class inherits all the methods from another class.

Inheritance is useful for code reusability: reuse properties and methods of an existing class when you create a new class.

Note: From the example above; The super() method refers to the parent class. By calling the super() method in the constructor method, we call the parent's constructor method and gets access to the parent's properties and methods.


Browser Support

Keyword
extends 49.0 13.0 45.0 9.0 36.0

Syntax

class childClass extends parentClass

Technical Details

JavaScript Version: ECMAScript 2015 (ES6)

Related Pages

JavaScript Tutorial: JavaScript Classes

JavaScript Tutorial: JavaScript ES6 (EcmaScript 2015)

JavaScript Reference: The super Keyword

JavaScript Reference: The constructor() method