The extends Keyword

The extends keyword in JavaScript is used to create a child class that inherits properties and methods from a parent class.

Let's first create a parent class:

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

Now, let's create a child class that extends the parent class:

class Dog extends Animal {
  // The Dog class inherits from Animal
}

This simple code means that the Dog class now inherits all the properties and methods from the Animal class.

Create a dog instance:

const dog = new Dog('Rex');

Call a method inherited from the parent:

console.log(dog.speak()); // Outputs: "Rex makes a noise."

The extends keyword creates an inheritance relationship where the child class (Dog) can access and use all the functionality defined in the parent class (Animal).