<!DOCTYPE HTML>
<html lang="zh-CN">
<head>
<meta charset="UTF-8">
<title>Bootstrap 3 的多级下拉菜单示例</title>
<script type="text/javascript" src="http://libs.baidu.com/jquery/1.9.0/jquery.js"></script>
<link rel="stylesheet" href="http://libs.baidu.com/bootstrap/3.0.3/css/bootstrap.min.css" rel="external nofollow" />
<script type="text/javascript" src="http://libs.baidu.com/bootstrap/3.0.3/js/bootstrap.min.js"></script>
<style type="text/css">
.dropdown-submenu {
position: relative;
}
.dropdown-submenu > .dropdown-menu {
top: 0;
left: 100%;
margin-top: -6px;
margin-left: -1px;
-webkit-border-radius: 0 6px 6px 6px;
-moz-border-radius: 0 6px 6px;
border-radius: 0 6px 6px 6px;
}
.dropdown-submenu:hover > .dropdown-menu {
display: block;
}
.dropdown-submenu > a:after {
display: block;
content: " ";
float: right;
width: 0;
height: 0;
border-color: transparent;
border-style: solid;
border-width: 5px 0 5px 5px;
border-left-color: #ccc;
margin-top: 5px;
margin-right: -10px;
}
.dropdown-submenu:hover > a:after {
border-left-color: #fff;
}
.dropdown-submenu.pull-left {
float: none;
}
.dropdown-submenu.pull-left > .dropdown-menu {
left: -100%;
margin-left: 10px;
-webkit-border-radius: 6px 0 6px 6px;
-moz-border-radius: 6px 0 6px 6px;
border-radius: 6px 0 6px 6px;
}
</style>
</head>
<body>
<div class="container">
<div class="row">
<div class="form-group">
<input type="hidden" name="category_id" id="category_id" value="" />
<div class="dropdown">
<a id="dLabel" role="button" data-toggle="dropdown" class="btn btn-white" data-target="#" href="javascript:;" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" ><span id="select-title">选择分类</span> <span class="caret"></span></a>
<ul class="dropdown-menu multi-level" role="menu" aria-labelledby="dropdownMenu">
<li><a href="javascript:;" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" data-index="1" data-title="一级菜单">一级菜单</a></li>
<li class="dropdown-submenu">
<a href="javascript:;" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" data-index="2" data-title="一级菜单">一级菜单</a>
<ul class="dropdown-menu">
<li><a data-index="2-1" href="javascript:;" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" data-title="二级菜单">二级菜单</a></li>
</ul>
</li>
<li class="dropdown-submenu">
<a tabindex="3" href="javascript:;" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" data-title="一级菜单">一级菜单</a>
<ul class="dropdown-menu">
<li><a tabindex="3-1" href="javascript:;" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" data-title="二级菜单">二级菜单</a></li>
<li class="divider"></li>
<li class="dropdown-submenu">
<a href="javascript:;" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" data-index="3-2" data-title="二级菜单">二级菜单</a>
<ul class="dropdown-menu">
<li><a href="javascript:;" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" data-index="3-2-1" data-title="三级菜单">三级菜单</a></li>
</ul>
</li>
</ul>
</li>
</ul>
</div>
</div>
</div>
</div>
<script type="text/javascript">
$('.dropdown li a').click(function(){
console.log(this);
title = $(this).attr("data-title");
id = $(this).attr("data-index");
$("#select-title").text(title);
$("#category_id").val(id);
})
</script>
</body>
</html>
参考：
https://www.jb51.net/article/128874.htm
https://www.cnblogs.com/stubborn-donkey/p/7248618.html