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<head>
<meta charset="UTF-8">
<title>javascript高级语法18-享元模式</title>
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<body>
<script>
/*享元模式是一个为了 提高性能（空间复杂度）的设计模式；
* 他使用于程序会生产大量的相类似的对象时 耗用大量内存的问题；
*
*/
function demo(){
//有一个城市要进行汽车登记
/*
* 制造商，型号，日期，所有者，车牌号，最近一次登记
*/
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;
}
}
// 装饰者，计算函数运行时间
var simpleProfiler2 = function(component){
this.component = component;
this.action = function(methodName){
var self= this;
var method = component[methodName];
//如果是函数那就进行装饰
if(typeof method == "function"){
var startDate = new Date().getTime();
method.apply(self.component,arguments);
var endDate = new Date().getTime();
alert(endDate - startDate);
}
}
}
//北京4150000全部要登记
var ca = new Array();
function addCar(){
this.begin = function(){
for(var i=0;i<4150000;i++){
ca.push(new Car("东风","雪铁龙","2017-5-16","张丹",
"京AM39385","2016-12-12"));
}
}
}
new simpleProfiler2(new addCar()).action("begin");
//耗费了大量时间和内存占用
}
// demo();
function xiangyuan(){
//1.内在状态
var Car = function(make,model,year,owner,tag,renewDate){
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
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;
}
}
//享元工厂
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;
}
}
})();
//北京4150000全部要登记
var test = new myCarInfo();
var startDate = new Date().getTime();
var ca = new Array();
for(var i=0;i<4150000;i++){
ca.push(test.createCar("东风","雪铁龙","2017-5-16","张丹",
"京AM39385","2016-12-12"));
}
var endDate = new Date().getTime();
alert(endDate - startDate);
}
xiangyuan();
</script>
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</html>
