bootstrap 多级下拉菜单

如上效果；

实现代码：

导入js和css：

    <link rel="stylesheet" href="http://cdn.static.runoob.com/libs/bootstrap/3.3.7/css/bootstrap.min.css">  
    <script src="http://cdn.static.runoob.com/libs/jquery/2.1.1/jquery.min.js"></script>
    <script src="http://cdn.static.runoob.com/libs/bootstrap/3.3.7/js/bootstrap.min.js"></script>

html code：

<div class="container">
    <div class="row">
        <div class="dropdown" >
            <a id="dLabel" role="button" data-toggle="dropdown" class="btn btn-success" data-target="#" href="/page.html">
                xx <span class="caret"></span>
            </a>
            <ul style="text-align: center" class="dropdown-menu multi-level" role="menu" aria-labelledby="dropdownMenu">
              <li class="dropdown-submenu">
                <a tabindex="-1" href="#">xx</a>
                <ul class="dropdown-menu">
                     <li style="text-align: center">
                      <a tabindex="-1" href="#">xx</a>
                     </li>
                     <li class="divider"></li>
                    <li style="text-align: center">
                    <a href="#">xx</a>
                   </li>
                </ul>
              </li>
            </ul>
        </div>
    </div>
</div>

css：

<style>
    
.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;
     0;
    height: 0;
    border-color: transparent;
    border-style: solid;
    border- 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>