Inheritance

Inheritance in JavaScript allows objects to inherit properties and methods from other objects, enabling the creation of hierarchies and the reuse of code.

One common way to achieve inheritance in JavaScript is through prototype chaining or using ES6 classes.

1. Prototype Chaining:

// Parent constructor function
function Animal(name) {
  this.name = name;
}

// Method shared by all instances of Animal
Animal.prototype.walk = function() {
  console.log(this.name + ' is walking.');
};

// Child constructor function
function Dog(name, breed) {
  Animal.call(this, name); // Call parent constructor
  this.breed = breed;
}

// Set up prototype chain
Dog.prototype = Object.create(Animal.prototype);
Dog.prototype.constructor = Dog;

// Method specific to Dog
Dog.prototype.bark = function() {
  console.log(this.name + ' is barking.');
};

// Create instances
var dog1 = new Dog('Buddy', 'Labrador');
dog1.walk(); // Output: Buddy is walking.
dog1.bark(); // Output: Buddy is barking.

In this example:

• Animal is the parent constructor function defining a basic animal.

• Dog is a child constructor function inheriting from Animal.

• Object.create(Animal.prototype) creates a new object with Animal.prototype as its prototype, establishing the prototype chain.

• Dog.prototype.constructor sets the constructor property of Dog.prototype to Dog (it's reset because it was lost when setting up the prototype chain).

2. ES6 Classes:

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

  walk() {
    console.log(`${this.name} is walking.`);
  }
}

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

  bark() {
    console.log(`${this.name} is barking.`);
  }
}

// Create instances
const dog1 = new Dog('Buddy', 'Labrador');
dog1.walk(); // Output: Buddy is walking.
dog1.bark(); // Output: Buddy is barking.

Here:

• class syntax provides a more structured way of defining constructors and methods.

• extends keyword allows Dog to inherit from Animal.

• super() is used to call the parent constructor within the child constructor.