js实现单例模式

http://my.oschina.net/u/1992917/blog/413263

var single = (function(){
   var unique;
   function getInstance(){
      if( unique === undefined ){
         unique = new Construct();
      }
      return unique;
   }
   function Construct(){
      // ... 生成单例的构造函数的代码
   }
   return {
      getInstance : getInstance
   }
})();