Inheritance with extends and super

The extends keyword is used to create a class as a child of another class. The super keyword is used to call the parent class’s constructor or methods. This allows classical inheritance in JavaScript.

Key Points

• extends sets up the prototype chain.
• super() must be called before accessing this in the child constructor.
• super.method() can call parent class methods.

Code Example

class Animal {
  constructor(name) {
    this.name = name;
  }
  speak() {
    console.log(`${this.name} makes a noise.`);
  }
}

class Dog extends Animal {
  constructor(name, breed) {
    super(name); // call parent constructor
    this.breed = breed;
  }
  speak() {
    super.speak(); // call parent method
    console.log(`${this.name} barks.`);
  }
}

const dog = new Dog("Rex", "German Shepherd");
dog.speak();
// "Rex makes a noise."
// "Rex barks."