Javascript显示和隐藏ul列表的方法

<ul id="rightNav">
 <li>
 <h2 class="rightNavItem"><a href="#">Show & Hide</a></h2>
 <ul>
 <li><a href="">Links etc here</a></li>
 </ul>
 </li>
</ul>
<script>
function enableRightNavExpand() {
 if (!document.getElementById) return false;
 if (!document.getElementById("rightNav")) return false;
 var nav = document.getElementById("rightNav");
 var navItem = nav.getElementsByTagName("li");
 for (var i = 0; i < navItem.length; i++){
  navItem[i].onclick=function() {
   if (this.className == "selected") {
    this.className = "";
   }
   else if (this.className == ""){
    this.className = "selected";
   }
  }
 }
}
</script>