JavaScript享元模式

通过两个例子的对比来凸显享元模式的特点：享元模式是一个为了提高性能(空间复杂度)的设计模式，享元模式可以避免大量非常相似类的开销。

第一实例，没有使用享元模式，计算所花费的时间和空间使用程度。

要求为：有一个城市要进行汽车的登记

（1）汽车类

/*** 制造商* 型号* 拥有者* 车牌号码* 最近一次登记日期*/var Car = function(make,model,year,owner,tag,renewDate){this.make = make;this.model = model;this.year = year;this.owner = owner;this.tag = tag;this.renewDate = renewDate;this.getMake = function(){return this.make;}}

（2）使用装饰者模式--计算函数的耗时

//装饰者 .. 计算函数的耗时var simpleProfiler = function(componet){this.componet = componet;this.action = function(methodName){var self = this;var method = componet[methodName];//如果是函数那就进行装饰if(typeof method == "function"){var startDate = new Date().getTime();//开始时间
                method.apply(self.componet,arguments);var endDate = new Date();//结束时间alert(endDate - startDate);                }}}

（3）具体的实例，现有4150000辆车需要登记

var ca = new Array();function addCar(){this.begin = function(){for (var i = 0; i < 4150000; i++) {ca.push(new Car("BMW","宝马","2017-10-18","","GBMW88","2017-10-19"));}}}new simpleProfiler(new addCar()).action("begin")

第二个例子：使用享元模式

（1）汽车类

/*** 制造商* 型号* 拥有者* 车牌号码* 最近一次登记日期*/var Car = function(make,model,year){this.make = make;this.model = model;this.year = year;this.getMake = function(){return this.make;}}

（2）单例模式的简单工厂

//单例模式的简单工厂var myCarInfo = function(){this.createCar = function(make,model,year,owner,tag,renewDate){var c = carInfoFactory(make,model,year);c["owner"] = owner;c["tag"] = tag;c["renewDate"] = renewDate;return c;}}var carInfoFactory = (function(){var carInfo = {};return function(make,model,year){if(carInfo[make+model+year]){return carInfo[make+model+year];}else{var newCar = new Car(make,model,year);carInfo[make+model+year] = newCar;return newCar;a}}})();

（3）现有4150000辆车需要登记

var test = new myCarInfo();var startDate = new Date().getTime();var ca = new Array();for (var i = 0; i < 4150000; i++) {ca.push(test.createCar("BMW","宝马","2017-10-18","","GBMW88","2017-10-19"))}var endDate = new Date();alert(endDate - startDate);