JavaScript设计模式之单例模式详解

/** * pre 单例模式 * 定义：保证一个类仅有一个实例，并提供一个访问它的全局访问点 * 应用：单例模式是一种常用的模式，有一些对象我们往往只需要一个， * 比如线程池、全局缓存、浏览器中的 window 对象等。 *///--------------singleton-01-------------/*写法1*/var Singleton = function(name){ this.name = name; this.instance = null;};Singleton.prototype.getName = function(){ alert(this.name);};Singleton.getInstance = function(){ if(!this.instance){  this.instance = new Singleton(name); } return this.instance;};var a = Singleton.getInstance("amy");var b = Singleton.getInstance("ben");alert(a === b);// ------------singleton-02----------------/*写法2*/var Singleton = function(name){ this.name = name;}Singleton.prototype.getName = function(){ return this.name;}Singleton.getInstance = (function(){ var instance = null; return function(name){  if(!instance){   instance = new Singleton(name);  }  return instance; }})();var a = Singleton.getInstance("amy");var b = Singleton.getInstance("ben");alert(a === b);// ------------singleton03-----------/*写法3*/var Singleton = (function(){ var instance; return function(name){  if(instance){   return instance;  }  this.name = name;  instance = this; }})();var a = new Singleton("amy");var b = new Singleton("ben");alert(a === b);//---------------- 示例 ---------------var getSingleton = function(fn) { var result; return function() {  if(!result) {   result = fn.apply(this, arguments);  }  return result; }};var getSingletonVip = (function() { var instance; return function(fn) {  return instance || (instance = fn.apply(this, arguments)); }})();var createLoginUser = function() { var div = document.createElement("div"); div.innerHTML = '这是登录框'; document.body.appendChild(div); return div;};var createInfoGrid = function() { var div = document.createElement("div"); div.innerHTML = '这是列表信息框'; document.body.appendChild(div); return div;};//--执行singleton1 var createUserDiv = getSingleton(createLoginUser);createUserDiv();createUserDiv();//--执行singleton2getSingletonVip(createLoginUser);getSingletonVip(createLoginUser);