js实现Tab选项卡切换效果(2)

*{
 padding:0px;
 margin:0px;
 list-style: none;
 font-size: 14px;
}
#tab{
 width:298px;
 height:120px;
 margin:10px;
 border:1px solid #eee;
 overflow: hidden;
}
.tab-nav{
 width:400px;
 position:relative;
 height:27px;

}
.tab-nav ul{
 position:absolute;
 width:301px;
 left:-1px;
 background-color: #f7f7f7;
}
.tab-nav li{
 float:left;
 width:58px;
 padding: 0 1px;
 height:36px;
 background-color: #f7f7f7;
 border-bottom: 1px solid #eee;
 text-align: center;
}
.tab-nav li.active{
 background-color: #fff;
 border-bottom-color:#fff;
 border-left: 1px solid #eee;
 border-right: 1px solid #eee;
 padding:0px;
 font-weight: bolder;
}
li a:link,li a:visited{
 text-decoration: none;
 color:#000;
}
#tab-contain .mod{
 margin:25px 6px 10px 6px;
}
#tab-contain .mod ul li{
 float: left;
 width:143px;
 height:25px;
 overflow: hidden;
}

function $(id){
 return typeof id==='string'?document.getElementById(id):id;
}
window.onload=function(){
 var navs=$('tab-nav').getElementsByTagName('li');
 var divs=$('tab-contain').getElementsByTagName('div');
 // alert(divs.length);
 if(navs.length!=divs.length){
  return;
 }
 for(var i=0;i<navs.length;i++){
  navs[i].title=i;
  navs[i].onmouseover=function(){
   for(var j=0;j<navs.length;j++){
    navs[j].className="";
    divs[j].style.display="none";

   }
   this.className="active";
   divs[this.title].style.display="block";
  }
 }

}