JavaScript reference

extends

Creates a subclass that inherits the parent's properties and methods.

Available since: ES2015

Syntax

class Child extends Parent { … }

Examples

A subclass gets the parent's methods and adds its own:

class Animal {
  constructor(name) {
    this.name = name;
  }
 
  describe() {
    return `${this.name} is an animal`;
  }
}
 
class Dog extends Animal {
  bark() {
    return `${this.name} says woof`;
  }
}
 
const rex = new Dog('Rex');
 
console.log(rex.describe());
console.log(rex.bark());

Output:

Rex is an animal
Rex says woof

Extending a built-in class:

class NotFoundError extends Error {
  constructor(what) {
    super(`${what} not found`);
    this.name = 'NotFoundError';
  }
}
 
console.log(String(new NotFoundError('User')));

Output:

NotFoundError: User not found

Notes

A class can extend only one class. If the subclass has its own constructor, it must call super(...) first.

In the tutorial

Inheritance — Class inheritance in JavaScript — extends, super, overriding methods and instanceof.

Thanks for reading!