jQuery实现点击向下展开的多级伸缩导航菜单

<html>
<head>
<title>可折叠展开的导航条</title>
<style>
body{margin:0;padding:0 0 12px 0;font-size:12px;line-height:22px;font-family:"\5b8b\4f53","Arial Narrow";background:#fff;}
form,ul,li,p,h1,h2,h3,h4,h5,h6{margin:0;padding:0;}
input,select{font-size:12px;line-height:16px;}
img{border:0;}
ul,li{list-style-type:none;}
a {color:#00007F;text-decoration:none;}
a:hover {color:#bd0a01;text-decoration:underline;}
.box {
width: 150px;
margin: 0 auto;
}
.menu{
overflow:hidden;
border-color: #C4D5DF;
border-style: solid;
border-width: 0 1px 1px;
}
/* lv1 */
.menu li.level1 a{
display: block;
height: 28px;
line-height: 28px;
 background:#EBF3F8;
font-weight:700;
color: #5893B7;
text-indent: 14px;
border-top: 1px solid #C4D5DF;
}
.menu li.level1 a:hover{text-decoration:none;}
.menu li.level1 a.current{background:#B1D7EF;}
/* lv2 */
.menu li ul{overflow:hidden;}
.menu li ul.level2{display:none;}
.menu li ul.level2 li a{
display: block;
height: 28px;
line-height: 28px;
background:#ffffff;
font-weight:400;
color: #42556B;
text-indent: 18px;
border-top: 0px solid #ffffff;
overflow: hidden;
}
.menu li ul.level2 li a:hover{
color:#f60;
}
</style>
<script src="jquery-1.6.2.min.js"></script>
<script>
$(document).ready(function(){
 $(".level1 > a").click(function(){
  $(this).addClass("current") //给当前元素添加"current"样式
  .next().show() //下一个元素显示
  .parent().siblings().children("a").removeClass("current")
  //父元素的兄弟元素的子元素<a>移除"current"样式
  .next().hide(); //它们的下一个元素隐藏
  return false;
 });
});
</script>
</head>
<body>
<div class="box">
 <ul class="menu">
  <li class="level1">
   <a href="#none">衬衫</a>
   <ul class="level2">
    <li><a href="#none">短袖衬衫</a></li>
    <li><a href="#none">长袖衬衫</a></li>
    <li><a href="#none">短袖T恤</a></li>
    <li><a href="#none">长袖T恤</a></li>
   </ul>
  </li>
  <li class="level1">
   <a href="#none">卫衣</a>
   <ul class="level2">
    <li><a href="#none">开襟卫衣</a></li>
    <li><a href="#none">套头卫衣</a></li>
    <li><a href="#none">运动卫衣</a></li>
    <li><a href="#none">童装卫衣</a></li>
   </ul>
  </li>
  <li class="level1">
   <a href="#none">裤子</a>
   <ul class="level2">
    <li><a href="#none">短裤</a></li>
    <li><a href="#none">休闲裤</a></li>
    <li><a href="#none">牛仔裤</a></li>
    <li><a href="#none">免烫卡其裤</a></li>
   </ul>
  </li>
 </ul>
</div>
</body>
</html>