javascript实现列表的点击展开折叠

 <script>
 window.onload = function()
 {
     //要折叠的区域
     var catalog = document.getElementById("div-id");
     //如果全部列表都添加折叠使用document.getElementsByTagName("ul");
     var childs  = catalog.getElementsByTagName("ul");
     for (var i = 0; i < childs.length; i++)
     {
         var liList = childs[i].childNodes;
         for (var j = 0; j < liList.length; j++)
         {
             if (liList[j].tagName == "LI")
             {
                 addEvent(liList[j]);
             }
         }
     }
 }
 function addEvent(o)
 {
     var as = o.getElementsByTagName("a");
     as[0].onclick = function(e)
     {
         var theEvent = window.event || e;
         var link = theEvent.srcElement ? theEvent.srcElement : theEvent.target;
         var uls  = link.parentNode.childNodes;
         for (var i = 0;i < uls.length;i++)
         {
             if (uls[i].tagName == "UL")
             {
                 if (uls[i].style.display == "none")
                 {
                     uls[i].style.display = "block";
                 }
                 else
                 {
                     uls[i].style.display = "none";
                 }
             }
          }
     }
 }  

以上是javascript简单的对列表实现点击展开折叠功能