JavaScript Object Inheritance

object.js

/**
 * Just a test for JavaScript object inheritance
 *
 * User: giemza
 * Date: 06.01.12
 * Time: 10:38
 */

// Human constructor, type is 'Function'
var Human = function(firstname, lastname) {
    // public fields, accessible from outside
    this.firstname = firstname;
    this.lastname = lastname;
    // private field, only accessible from inside, e.g., getFullname function
    var fullname = firstname + ' ' + lastname;

    this.getFullname = function() {
        return fullname;
    }
};

// Human public method (overrides toString from Object)
Human.prototype.toString = function() {
    return this.firstname + ' ' + this.lastname;
};

// new human instance, type is 'Object'
var adam = new Human('Adam', 'Riese');
// another human instance
var jan = new Human('Jan', 'Padawan');

console.log('firstname + lastname: ' + adam.firstname + ' ' + adam.lastname);
// prints: firstname + lastname: Adam Riese

console.log('adam.fullname: ' + adam.fullname);
// prints: adam.fullname: undefined

console.log('adam.getFullname(): ' + adam.getFullname());
// prints: adam.getFullname(): Adam Riese

console.log('adam.toString(): ' + adam);
// prints: adam.toString(): Adam Riese

console.log('jan.toString(): ' + jan);
// prints: jan.toString(): Jan Padawan

// ### Inheritance ###

// Hacker constructor, type Function
var Hacker = function(firstname, lastname) {
    Human.apply(this, [firstname, lastname]);
    // calls the prototypes constructor (like super() in Java)
//    Hacker.prototype.__proto__.constructor(firstname, lastname);
//    Hacker.prototype.firstname = firstname;
//    Hacker.prototype.lastname = lastname;
    // public field
    this.hacks = true;
};

// setting the prototype of the Hacker's prototype to the prototype of the Human
//Hacker.prototype.__proto__ = Human.prototype;
Hacker.prototype = new Human();
//Hacker.prototype.constructor = Hacker;

// Hacker public method (overrides and calls Human.toString())
Hacker.prototype.toString = function() {
//    return Hacker.prototype.__proto__.toString.call(this) + ' hacks: ' + this.hacks;
    return Human.prototype.toString.call(this) + ' hacks: ' + this.hacks;
};

// new Hacker instance, type Object
var stefan = new Hacker('Stefan', 'Nafets');

console.log('stefan.toString(): ' + stefan);
// prints: stefan.toString(): Stefan Nafets hacks: true

console.log('stefan.hacks: ' + stefan.hacks);
// prints: stefan.hacks: true

console.log('stefan.getFullname(): ' + stefan.getFullname());
// prints: Stefan Nafets