重写setTimeout扩展参数

 1 //判断函数行参长度来决定是否需要重写setTimeout，ie8以下为undefined
 2 if(window.setTimeout.length == undefined){
 3     var __sto = window.setTimeout;
 4     window.setTimeout = function(callback,timeout,param){
 5         var args = Array.prototype.slice.call(arguments,2);
 6         __sto(function(){
 7             callback.apply(null,args);
 8         },timeout);
 9     };
10 }