JavaScript Object Inheritance Models

There are lots of ways to create objects in JavaScript and do inheritance, and the creativity usually extrapolates what I consider sane, but these are the ones that I use the most. I will call models here.

And note that this is ES5.

Pseudoclassical

JavaScript is a prototypal, class-free. The pseudoclassical is a way to give JavaScript a feel of the traditional object-oriented languages.

#!/usr/bin/env node

"use strict";

// constructor
var Car = function (name) {
    this.name = name;

    this.turn_on = function () {
        console.log('turn on');
    }
}

Car.prototype.get_name = function () {
    return this.name;
}

Car.prototype.turn_on = function () {
    console.log('push on');
}

// child constructor
var ElectricCar = function (n, bm) {
    this.name = n;
    this.battery_model = bm;
}

// inherit from Car
ElectricCar.prototype = new Car();

// augment child prototype
ElectricCar.prototype.get_battery_model = function () {
    return this.battery_model;
}

// instantiating
var lada = new Car('Lada');
var tesla = new ElectricCar('Tesla');

console.log(lada.name);
console.log(tesla.name);
tesla.turn_on();

Prototypal

The gist below uses Object.create(). Douglas Crockford, in his book JavaScript: The Good Parts, suggests augmenting Object in order to create a new object that uses an old object as a prototype. His proposal is:

if (typeof Object.create !== 'function') {
    Object.create = function (o) {
        var F = function () {};
        F.prototype = o;
        return new F();
    }
}

This isn't needed anymore. The book is from 2008. In 2011, ECMAScript 5.1 standardized it.

#!/usr/bin/env node

"use strict";

var lada = {
    name: 'Lada',
    turn_on: function() {
        console.log(this.name + ' on');
    },
};

var tesla = Object.create(lada);
tesla.name = 'Tesla';
tesla.recharge = function () {
    console.log(this.name + ' battery recharged');
};

console.log(lada.name);
console.log(tesla.name);
tesla.turn_on();
tesla.recharge();

Output

Both should output:

$ node file.js
Lada
Tesla
Tesla on
Tesla battery recharged
$