单例

var mySingleton = (function(){var instance;function init(){var privateRandomNumber = Math.random();return{getRandomNumber:function(){return privateRandomNumber;}}};return {getInstance :function(){if(!instance){instance = init();}return instance;}};})();var SA = mySingleton.getInstance();var SB = mySingleton.getInstance();alert(SA.getRandomNumber() === SB.getRandomNumber());