javascript实现tab切换效果

这个功能是很久之前实现的，现在发上来，很长一段时间没更新博客了，真惭愧。这个JS代码还有很多修改的空间，先发上来，以后再发个更新的版本吧。

这是效果图：

【HTML代码】

<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>

【js】

/**
 * 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");
}

【CSS】

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}