method declared outside of class deceleration could not be inherited by child class in javascript

Question

// declared class vehicle
function Vehicle(make,model,year){
  this.make=make
  this.model=model
  this.year=year

}
// 2 - Add a function to the Vehicle prototype called start which returns the string //"VROOM!"
 Vehicle.prototype.start=function(){
  return "VROOM!"
}

// declared child class car
function Car(make,model,year){
  Vehicle.apply(this,arguments)
  this.numWheels=4

}
// assigning the constructor
Car.prototype.constructor=Object.create(Vehicle.constructor)
// changing the pointing of constructor back to car
Car.prototype.constructor=Car;
var sedan=new Car("Tractor", "John Deere", 1999)
console.log(sedan.start()) 
//sedan.start() gives error but if i declare it inside vehicle class does not 

Answer 1

To get Car() to inherit the methods defined on Vehicle()'s prototype, you can simply use:

Car.prototype = Object.create(Vehicle.prototype);

Here Object.create() method is used to create a new object and make it the value of Car.prototype. The new object has Vehicle.prototype as its prototype and will therefore inherit all the methods available on Vehicle.prototype. So, there is no need to use the below logic:

// assigning the constructor
Car.prototype.constructor=Object.create(Vehicle.constructor)

DEMO:

// declared class vehicle
function Vehicle(make, model, year) {
  this.make = make
  this.model = model
  this.year = year
}

// 2 - Add a function to the Vehicle prototype called start which returns the string //"VROOM!"
Vehicle.prototype.start = function() {
  return "VROOM!"
}

// declared child class car
function Car(make, model, year) {
  Vehicle.apply(this, arguments)
  this.numWheels = 4
}
Car.prototype = Object.create(Vehicle.prototype);
Car.prototype.constructor = Car;
var sedan = new Car("Tractor", "John Deere", 1999)
console.log(sedan.start())

A better approach using Classes:

ECMAScript 2015 introduces class syntax to JavaScript as a way to write reusable classes using easier, cleaner syntax, which is more similar to classes in C++ or Java. Here we'll convert the Vehicle and Car example from prototypal inheritance to classes, to show you how it's done.

DEMO:

class Vehicle {
  constructor(make, model, year) {
    this.make = make;
    this.model = model;
    this.year = year;
  }
  start() {
    return "VROOM!"
  };
}

class Car extends Vehicle {
  constructor(make, model, year) {
    super(); // Now 'this' is initialized by calling the parent constructor.
  }
  bonet() {
    return "VROOM2!"
  };
}

var sedan = new Car("Tractor", "John Deere", 1999)
console.log(sedan.start())
console.log(sedan.bonet())