JavaScript, how to extend a class

Nov 15, 2020

Learn how to extend a class in JavaScript with the extends keyword, so a subclass like Fish inherits methods from a base Animal class and adds its own.

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JavaScript inheritance works using classes.

Suppose you have a class Animal:

class Animal {
  breathe() {
    //...
  }
}

All animals breathe. I think. We can take this as a general rule for this example.

But not animals walk. Some animals can fly, etc.

So we can extend this class to form species, and we extend from the base class to inherit the breathe() method, and provide specific methods and properties:

class Fish extends Animal {
  swim() {
    //...
  }
}

class Bird extends Animal {
  fly() {
    //...
  }
}

You can instantiate an instance of a class using the new keyword, and you end up with an object:

const randomAnimal = new Animal()
const hummingbird = new Bird()

Tagged: JavaScript · All topics

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