var bikeFactory = {
	createBike : function(model){
		var bike;
		switch(model){
			case ‘The Speedster‘:
				bike = new Speedster();
				break;
			case ‘The Lowerster‘:
				bike = new Lowerster();
				break;
			case "Other":
			default:
				bike = new Other();
				break;
		}
		return bike;
	}	
}
var BicycleShop = function(){};
//让实现这个接口的类来决定实例化哪个类
BicycleShop.prototype = {
	sellPrototype:function(model){
		var bicycle = bikeFactory.createBike(model);     
        return bicycle;
	}
}