hmtl文件
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>下拉菜单案例</title>
<style type="text/css">
* {
margin: 0;
padding: 0;
}
ul {
list-style: none;
}
.wrap {
330px;
height: 30px;
margin: 100px auto 0;
padding-left: 10px;
background:pink;
}
.wrap li {
background:#0f0;
}
.wrap > ul > li {
float: left;
margin-right: 10px;
position: relative;
}
.wrap a {
display: block;
height: 30px;
100px;
text-decoration: none;
color: #000;
}
.wrap li ul {
position: absolute;
top: 30px;
display: none;
}
</style>
<script src="jquery-1.12.4.js"></script>
<script>
$(function(){
//mouseover：鼠标经过事件
//mouseout:鼠标离开事件
//mouseenter:鼠标进入事件
//mouseleave：鼠标离开事件
var $li = $(".wrap>ul>li");
//给li注册鼠标经过事件，让自己的ul显示出来
$li.mouseenter(function(){
//找到所有的儿子，并且还得是ul
$(this).children("ul").show();
})
$li.mouseleave(function(){
$(this).children("ul").hide();
})
})
</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11</a></li>
<li><a href="javascript:void(0);">二级菜单12</a></li>
<li><a href="javascript:void(0);">二级菜单13</a></li>
</ul>
</li>
<li>
<a href="javascript:void(0);">一级菜单2</a>
<ul>
<li><a href="javascript:void(0);">二级菜单21</a></li>
<li><a href="javascript:void(0);">二级菜单22</a></li>
<li><a href="javascript:void(0);">二级菜单23</a></li>
</ul>
</li>
<li>
<a href="javascript:void(0);">一级菜单3</a>
<ul>
<li><a href="javascript:void(0);">二级菜单31</a></li>
<li><a href="javascript:void(0);">二级菜单32</a></li>
<li><a href="javascript:void(0);">二级菜单33</a></li>
</ul>
</li>
</ul>
</div>
</body>
</html>