下拉菜单特效怎么做点击后改变箭头的方向

[kyou5478]

效果是点击后右边的箭头方向往下的，附上JS代码

<script type=text/javascript><!--
var LastLeftID = "";
function menuFix() {
 var obj = document.getElementById("nav").getElementsByTagName("li");
 
 for (var i=0; i<obj.length; i++) {
  obj[i].onmouseover=function() {
   this.className+=(this.className.length>0? " ": "") + "sfhover";
  }
  obj[i].onMouseDown=function() {
   this.className+=(this.className.length>0? " ": "") + "sfhover";
  }
  obj[i].onMouseUp=function() {
   this.className+=(this.className.length>0? " ": "") + "sfhover";
  }
  obj[i].onmouseout=function() {
   this.className=this.className.replace(new RegExp("( ?|^)sfhover\\b"), "");
  }
 }
}
function DoMenu(emid)
{
 var obj = document.getElementById(emid); 
 obj.className = (obj.className.toLowerCase() == "expanded"?"collapsed":"expanded");
 
 LastLeftID = emid;
}
function GetMenuID()
{
 var MenuID="";
 var _paramStr = new String(window.location.href);
 var _sharpPos = _paramStr.indexOf("#");
 
 if (_sharpPos >= 0  &&  _sharpPos < _paramStr.length - 1)
 {
  _paramStr = _paramStr.substring(_sharpPos + 1, _paramStr.length);
 }
 else
 {
  _paramStr = "";
 }
 
 if (_paramStr.length > 0)
 {
  var _paramArr = _paramStr.split("&");
  if (_paramArr.length>0)
  {
   var _paramKeyVal = _paramArr[0].split("=");
   if (_paramKeyVal.length>0)
   {
    MenuID = _paramKeyVal[1];
   }
  }
  /*
  if (_paramArr.length>0)
  {
   var _arr = new Array(_paramArr.length);
  }
  
  //取所有#后面的，菜单只需用到Menu
  //for (var i = 0; i < _paramArr.length; i++)
  {
   var _paramKeyVal = _paramArr[i].split('=');
   
   if (_paramKeyVal.length>0)
   {
    _arr[_paramKeyVal[0]] = _paramKeyVal[1];
   }  
  }
  */
 }
 
 if(MenuID!="")
 {
  DoMenu(MenuID)
 }
}
GetMenuID(); //*这两个function的顺序要注意一下，不然在Firefox里GetMenuID()不起效果
menuFix();

--></script>

[___紫菜]

切换成另一张图片

[Kean_11]

点击事件里添加切换图标操作

[杨小事er]

用css精灵图啊，鼠标点击切换坐标

[不断学习的ITer]

切换div背景图片的position

[木头海上漂]

切换class，写俩个class