描述：鼠标放在一级导航的时候。二级导航缓慢显示。鼠标离开之后，二级导航缓慢隐藏。鼠标经过的时候，如果二级菜单还没有完全打开或者隐藏，则或停止当前动画。使用的jQuery的版本是1.8的。
示例代码：
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>缓慢下拉菜单</title>
<style type="text/css">
* {
margin: 0;
padding: 0;
}
ul {
list-style: none;
}
.wrap {
width: 330px;
height: 30px;
margin: 100px auto 0;
padding-left: 10px;
background-image: url(images/bg.jpg);
}
.wrap li{
background-image: url(images/libg.jpg);
}
.wrap > ul > li {
float: left;
margin-right: 10px;
position: relative;
}
.wrap a {
display: block;
height: 30px;
width: 100px;
text-decoration: none;
color: #000;
line-height: 30px;
text-align: center;
}
.wrap li ul {
position: absolute;
top: 30px;
display: none;
}
</style>
<script src="../jquery.min.js"></script>
<script>
$(window).ready(function () {
var jqli = $(".wrap>ul>li");
jqli.mouseenter(function () {
$(this).children("ul").stop().slideDown(200);
});
jqli.mouseleave(function () {
$(this).children("ul").stop().slideUp(200);
});
})
</script>
</head>
<body>
<div class="wrap">
<ul>
<li>
<a href="javascript:void(0);">一级菜单1</a>
<ul>
<li><a href="javascript:void(0);">二级菜单1</a></li>
<li><a href="javascript:void(0);">二级菜单2</a></li>
<li><a href="javascript:void(0);">二级菜单3</a></li>
</ul>
</li>
<li>
<a href="javascript:void(0);">一级菜单1</a>
<ul>
<li><a href="javascript:void(0);">二级菜单1</a></li>
<li><a href="javascript:void(0);">二级菜单2</a></li>
<li><a href="javascript:void(0);">二级菜单3</a></li>
</ul>
</li>
<li>
<a href="javascript:void(0);">一级菜单1</a>
<ul>
<li><a href="javascript:void(0);">二级菜单1</a></li>
<li><a href="javascript:void(0);">二级菜单2</a></li>
<li><a href="javascript:void(0);">二级菜单3</a></li>
</ul>
</li>
</ul>
</div>
</body>
</html>