Inheritance

Inheritance allows new classes (or constructor functions) to be created based on existing classes. This enables the child class to reuse methods and properties from a parent class, providing flexibility and code reuse.

Example:

// Parent class
function Vehicle(make, model, year) {
    this.make = make;
    this.model = model;
    this.year = year;
}

// Method shared by all vehicles
Vehicle.prototype.info = function() {
    console.log("This is a " + this.year + " " + this.make + " " + this.model);
};



// Child class inheriting from Vehicle
function Car(make, model, year, color) {
    Vehicle.call(this, make, model, year); // Call parent constructor
    this.color = color;
}

// Inherit methods from Vehicle
Car.prototype = Object.create(Vehicle.prototype);
Car.prototype.constructor = Car;

// Additional method for Car class
Car.prototype.drive = function() {
    console.log("Driving the " + this.color + " " + this.make + " " + this.model);
};

// Create instances
var myCar = new Car("Renault", "Kwid", 2024, "blue");
var anotherCar = new Car("Honda", "Civic", 2023, "red");

// Call methods
myCar.info();       // Outputs: "This is a 2024 Renault Kwid"
myCar.drive();      // Outputs: "Driving the blue Renault Kwid"
anotherCar.info();  // Outputs: "This is a 2023 Honda Civic"
anotherCar.drive(); // Outputs: "Driving the red Honda Civic"

Explanation:

• We have a parent class Vehicle with a method info.
• The child class Car inherits from Vehicle using prototype-based inheritance.
• Car introduces its own method drive.
• Instances of Car can access methods from both Vehicle and Car classes, and they also inherit shared properties from Vehicle.

Using extend keyword

The extends keyword is used to create a child class based on a parent class. This keyword facilitates the child class in inheriting all the properties and behavior (methods) of its parent class.

Example:

// Using extend keyword
class Parent {
    constructor(name) {
        this.name = name;
    }

    greet() {
        console.log(`Hello, ${this.name}!`);
    }
}

class Child extends Parent {
    constructor(name, age) {
        super(name); // Call the constructor of the Parent class
        this.age = age;
    }

    introduce() {
        console.log(`My name is ${this.name} and I am ${this.age} years old.`);
    }
}

const child = new Child("Rajesh", 10);
child.greet();      // Outputs: "Hello, Rajesh!"
child.introduce();  // Outputs: "My name is Alice and I am 10 years old."