design pattern

gistfile1.js

//
// singleton pattern
//

var Singleton = (function(){
	var instance;
	return function(){
		if(instance){
			return instance;
		};
		instance = this;
	}
})();

var sing1 = new Singleton();
var sing2 = new Singleton();

console.log(sing1 === sing2) // true

Singleton.prototype.test = 'test';
var sing3 = new Singleton();

console.log(sing3.test); // test
console.log(sing1.test); // test



//
// factory pattern
//

function CarMaker(){};

CarMaker.prototype.drive = function(){
	return 'Vroom, I have '+ this.doors + ' doors';
};

CarMaker.factory = function(type){
	var constr = type,newcar;
	

	if(typeof CarMaker[constr] !== 'function'){
		throw{
			name:"error",
			message:constr + ' doesn\'t exist'
		}
	};
	
	if(typeof CarMaker[constr].prototype.drive !== 'function'){
		　CarMaker[constr].prototype = new CarMaker();
	};
	
	console.log('a');
	newcar = new CarMaker[constr]();
	return newcar;
};

//--------------------------------------

CarMaker.Compact = function(){
	this.doors = 4;
};

CarMaker.Convertible = function(){
	this.doors = 2;
};

CarMaker.SUV = function(){
	this.doors = 17;
};

//--------------------------------------

var corolla = CarMaker.factory('Compact');