The super Keyword

The super keyword in JavaScript is used to access and call functions on an object's parent class. It is primarily used within class inheritance to call methods or constructors from the superclass.

Using super in a constructor

When extending a class, you must call super() inside the subclass constructor before using this. This calls the parent class constructor.

class Animal {
  constructor(name) {
    this.name = name;
  }
}

class Dog extends Animal {
  constructor(name, breed) {
    super(name);          // Call parent constructor
    this.breed = breed;
  }
}

const myDog = new Dog('Max', 'Golden Retriever');
console.log(myDog.name);  // Output: Max
console.log(myDog.breed); // Output: Golden Retriever

Using super to call parent methods

Within subclass methods, super.methodName() calls the parent class method, allowing you to extend or customize behavior.

class Animal {
  speak() {
    return 'Animal makes a sound';
  }
}

class Dog extends Animal {
  speak() {
    const parentSound = super.speak();  // Call parent method
    return parentSound + ' and Dog barks';
  }
}

const myDog = new Dog();
console.log(myDog.speak());  // Output: Animal makes a sound and Dog barks

Key points to remember:

• super() calls the parent constructor.
• super.method() calls a method from the parent class.
• Use super only in classes that extend another class.
• Always call super() before using this in constructors.