重写setTimeout扩展参数

 //判断函数行参长度来决定是否需要重写setTimeout，ie8以下为undefined
 if(window.setTimeout.length == undefined){
     var __sto = window.setTimeout;
     window.setTimeout = function(callback,timeout,param){
         var args = Array.prototype.slice.call(arguments,2);
         __sto(function(){
             callback.apply(null,args);
         },timeout);
     };
 }