Javascript Class Inheritance

Class inheritance in Javascript

Class inheritance in Javascript¶

Inheritance is the procedure in which one class inherits the attributes and methods of another class.
It provides code reusability
It gives better maintainability of the code
Javascript uses extends keyword to inherit the class.
Javascript uses super keyword to call the parent class method.

A quick example¶

Let's write some code to represent the different types cars i.e Audi and Tesla.
As, we know Audi and Tesla both has common properties and functionalities.
so, we can have a base class with common properties and functionalities. Let's name it as Car
The other two classes Audi and Tesla can inherit these properties and can add additional implementations.

class Car {
    constructor(color, model, makeYear, fuelType){
        this.color = color;
        this.model = model;
        this.makeYear = makeYear;
        this.fuelType = fuelType;
    }

    start(){
        return `started`;
    }

    stop(){
        return `stopped`
    }
}

class Audi extends Car{
    constructor(color, model, makeYear){
        super(color, model, makeYear, 'Petrol')
    }
}

class Tesla extends Car{
    constructor(color, model, makeYear){
        super(color, model, makeYear, 'Electric')
        this.autoPilotMode = false;
    }

    setAutoPilotMode(mode){
        this.autoPilotMode = mode;
        return this.autoPilotMode;
    }

    startAutoPilotMode(){
        return this.setAutoPilotMode(true);
    }

    stopAutoPilotMode(){
        return this.setAutoPilotMode(false);
    }
}

from the above code, we can see that classes Audi, Tesla both inherited the prperties from class Car.
We have implemented extra funcionaliy "auto pilot mode" on class Tesla.
Let's create objects for both cars Audi and Tesla

// create audi object
let audi_a4 = new Audi('Blue', 'A4', 2022);
console.log(audi_a4.start())
// output: started
console.log(audi_a4.color)
// output: Blue
// create tesla object
let tesla = new Tesla('Red', 'S', 2022);
console.log(tesla.start())
// output: started
console.log(tesla.startAutoPilotMode())
// output: true

Like above code we can re-use the properties from parent class and implement additional properties/functionalities.