var curIndex=0;
    //时间间隔 单位毫秒
    var timeInterval=12000;
    var arr=new Array();
    arr[0]="../images/banner/5.jpg";
    arr[1]="../images/banner/1.jpg";
    arr[2]="../images/banner/2.jpg";
    arr[3]="../images/banner/3.jpg";
    arr[4]="../images/banner/4.jpg";
   setInterval(changeImg,timeInterval);
   function changeImg()
   {
       var obj=document.getElementById("obj");
      if (curIndex==arr.length-1) 
      {
            curIndex=0;
      }
      else
      {
         curIndex+=1;
      }
      obj.src=arr[curIndex];
   }