js implementation of tab switching effect example_javascript skills

<div id="menu">
<!--tag标题-->
  <ul id="nav">
    <li><a href="#" class="selected">tab1</a></li>
    <li><a href="#" class="">tab2</a></li>
    <li><a href="#" class="">tab3</a></li>
    <div style="clear:both"></div>
  </ul>
<!--二级菜单-->
  <div id="menu_con">
    <div class="tag" style="display:block">
      这是TAB切换效果区域1
     </div> 
    <div class="tag" style="display:none">
      这是TAB切换效果区域2  
     </div> 
    <div class="tag" style="display:none">
      这是TAB切换效果区域3
    </div> 
</div>
</div>

/**
 * tabs
 * @author  橡树小屋
 */
var tabs=function(){
  function tag(name,elem){
    return (elem||document).getElementsByTagName(name);
  }
  //获得相应ID的元素
  function id(name){
    return document.getElementById(name);
  }
  function first(elem){
    elem=elem.firstChild;
    return elem&&elem.nodeType==1? elem:next(elem);
  }
  function next(elem){
    do{
      elem=elem.nextSibling; 
    }while(
      elem&&elem.nodeType!=1 
    )
    return elem;
  }
  return {
    set:function(elemId,tabId){
      var elem=tag("li",id(elemId));
      var tabs=tag("div",id(tabId));
      var listNum=elem.length;
      var tabNum=tabs.length;
      for(var i=0;i<listNum;i++){
          elem[i].onclick=(function(i){
            return function(){
              for(var j=0;j<tabNum;j++){
                if(i==j){
                  tabs[j].style.display="block";
                  //alert(elem[j].firstChild);
                  elem[j].firstChild.className="selected";
                }
                else{
                  tabs[j].style.display="none";
                  elem[j].firstChild.className="";
                }
              }
            }
          })(i)
      }
    }
  }
}();
window.onload=function(){
  tabs.set("nav","menu_con");
}

body{ background:#FFF;}
a{color:#585858}
#menu{width:360px;}
/*-------------------nav样式----------------------*/
#menu #nav {display:block;width:100%;padding:0;margin:0;list-style:none;
 background:url(../images/bg.gif)}
#menu #nav li {float:left;width:120px;}
#menu #nav li a {display:block;line-height:27px;text-decoration:none;padding:0 0 0 5px; text-align:center}
 
/*-------------------列表标题样式----------------------*/
#menu_con{ width:358px; height:135px;border:1px solid #BF9660; border-top:none}
.selected{background:url(../images/tag_bg.gif);}
.clear{ clear:both}