Classical Inheritance in Object Oriented JavaScript

classical-inheritance

/**
* (Pseudo)Classical Inheritance in JavaScript
*/

// Helpers and polyfills

/**
* Copies object's prototype properties
* to another object's prototype
*/
function inherits (ctor, superCtor) {
  ctor.super_ = superCtor;
  ctor.prototype = Object.create(superCtor.prototype, {
    constructor: {
      value: ctor,
      enumerable: false,
      writable: true,
      configurable: true
    }
  });
}

/**
*  Polyfill for Object.create()
*/
if ( typeof Object.create !== 'function' ) {
  Object.create = function(o, props) { 
		function F() {}
		F.prototype = o; 
		result = new F(); 
		if ( typeof(props) === "object" ) {
			for (var prop in props) { 
				if (props.hasOwnProperty((prop))) { 
					result[prop] = props[prop].value;
				} 
			} 
		} 
		return result;
	};
}

// SuperClass

var Orb = function(name) {
	this.name = name;
};

Orb.prototype.spin = function() {
	console.log(this.name + ' is spinning around!');
};

Orb.prototype.circle = function() {
	console.log(this.name + ' is circling around the Sun!');
};

// Planet

var Planet = function(name) {
	//this.name = name;
	Planet.super_.call(this, name);
};

inherits(Planet, Orb);

// Moon Class

var Moon = function(name, planet) {
	//this.name = name;
	Moon.super_.call(this, name);
	this.planetName = planet.name;
};

inherits(Moon, Planet);

Moon.prototype.circle = function() {
	console.log(this.name + ' is circling around the ' + this.planetName);
};

// Usage

var earth = new Planet("Earth");
var moon = new Moon("Moon", earth);
earth.spin();
earth.circle();
moon.spin();
moon.circle();
var saturn = new Planet("Saturn");
var titan = new Moon("Titan", saturn);
titan.spin();
titan.circle();