用JavaScript實現一個單例模式

單例模式的基本結構：

MyNamespace.Singleton = function() {return {};}();

比如：

MyNamespace.Singleton = (function() {return     {     // Public members.publicAttribute1: true,publicAttribute2: 10,publicMethod1: function() {...},publicMethod2: function(args)     {...}};})();

但是，上面的Singleton在代碼一載入的時候就已經建立了，怎麼消極式載入呢？採用下面這種模式：

MyNamespace.Singleton = (function() {function constructor()     {     // All of the normal singleton code goes here....}return     {getInstance: function()         {// Control code goes here.}}})();

具體來說，把建立單例的代碼放到constructor裡，在首次調用的時候再執行個體化：

完整的代碼如下：

MyNamespace.Singleton = (function() {var uniqueInstance; // Private attribute that holds the single instance.function constructor()     {     // All of the normal singleton code goes here....}return     {getInstance: function()         {if(!uniqueInstance) {             // Instantiate only if the instance doesn't exist.    uniqueInstance = constructor();}return uniqueInstance;}}})();