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The JavaScript Interview Handbook: 100+ Interview Questions

Solution Review: ES6 Inheritance

This lesson will explain the solution to the problem in the previous lesson.

We'll cover the following...

Solution #

Javascript (babel-node)
class Vehicle {                            
    constructor(fuel) { this.fuel = fuel; }      
    turnOn() { 
        console.log("Turned on")
    }
    turnOff(){
        console.log("Turned off")
    }                                      
}
 
class Car extends Vehicle {       
    constructor(fuel,isparked) {
        super(fuel);                           
        this.isparked = isparked
    }
    turnOn(){
        if ( this.fuel >= 500 ) {
            super.turnOn()
        }else{
            console.log("Refill Fuel")
        }
    }
    turnOff(){
        if(this.isparked == true){
            super.turnOff()
        }else{
            console.log("Car not parked")
        }
    }                               
}
var car1 = new Car(1000,true)
var car2 = new Car(400,true)
var car3 = new Car(1500,false)
car1.turnOn()
car1.turnOff()
car2.turnOn()
car2.turnOff()
car3.turnOn()
car3.turnOff()

Explanation #

Let’s start by discussing the implementation of the Vehicle class first.

  • On line 2, we are defining the constructor. It initializes the fuel property by setting it equal to the parameter passed.

    constructor(fuel) { this.fuel = fuel; }

  • On line 3, we are implementing the turnOn function. It displays the message Turned on.

 ...