JavaScript ClassextendsKeyword
JavaScript ClassExamples
Examples
The following example creates a class "Example" that inherits the "Site" class:
class Site {
constructor(name) {
this.sitename = name;
}
present() {
return 'I like' + this.sitename;
}
}
class Example extends Site {
constructor(name, age) {
super(name);
this.age = age;
}
show() {
return this.present() + ', it was created in' + this.age + 'year.';
}
}
let noob = new Example("Example", 5);
document.getElementById("demo").innerHTML = noob.show();
Try it Yourself »
Definition and Usage
The extends keyword is used to create a class that is a child class of another class.
The child class inherits all methods from another class.
Inheritance is useful for code reusability: reuse the properties and methods of an existing class when you create a new class.
The super() method refers to the parent class's constructor.
By calling the super() method in the constructor, we call the parent class's constructor, so we can access the parent class's properties and methods.
Syntax
class childClass extends parentClass
Technical Details
| JavaScript Version: | ECMAScript 2015 (ES6) |
Browser Support
extends is an ECMAScript6 (ES6) feature.
ES6 (JavaScript 2015) is supported in all current major browsers.
| Chrome | Edge | Firefox | Safari | Opera |
| Yes | Yes | Yes | Yes | Yes |
Internet Explorer 11 or older versions of IE do not support the extends keyword.
Other Extensions