Inheritance

Inheritance lets you create new classes that build on existing ones. Use it to share behavior when classes have a clear is-a relationship.

What inheritance is

• A child class extends a parent class.
• The child is a more specific version of the parent.

extends

• Use extends to inherit behavior and state.

class Animal {
  speak() {
    console.log("Some sound");
  }
}

class Dog extends Animal {
  speak() {
    console.log("Woof");
  }
}

super

• Call super() in the child constructor to run the parent constructor.
• Use super.methodName() to reuse parent methods.

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

class Dog extends Animal {
  constructor(name) {
    super(name);
  }
  speak() {
    super.speak(); // optional: call parent behavior
    console.log(`${this.name} barks`);
  }
}

Method overriding

• Child classes can replace inherited methods.
• Use overriding when behavior truly differs.

Inheritance cautions

• Avoid deep hierarchies—they become hard to change.
• Prefer composition over inheritance when:
  • Behavior varies a lot between instances.
  • You need to mix features (composition is more flexible).