jquery 定時器 調用函數時傳參

 jquery 定時器 調用函數時傳參
var li=$('.first>li:first-child');
 var index=0;
 var s=$('.first>li');
  function gundong(a,b){
          // console.log(b.length);
           index++;
      if(index>b.length-4){
          index=0
      }
      a.animate({marginTop:-35*index+"px"});
  }

 var sto = setInterval;
 window.setInterval = function(callback,timeout,param){
     var args = Array.prototype.slice.call(arguments,2);
     var _cb = function(){
         callback.apply(null,args);
     };
     sto(_cb,timeout);
 };
var first= setInterval(gundong,4000,li,s);