bootstrap下拉菜单使用方法解析

Bootstrap框架中的下拉菜单组件是一个独立的组件，具体来学习一下

下拉菜单（Dropdown）

☑ LESS版本：对应的源文件dropdowns.less

<h3>示例1</h3>
<div class="navbar navbar-default" id="navmenu">
  <a rel="nofollow noopener noreferrer" href="##" class="navbar-brand">W3cplus</a>
  <ul class="nav navbar-nav">
    <li class="dropdown">
      <a rel="nofollow noopener noreferrer" href="##" data-toggle="dropdown" class="dropdown-toggle" role="button" id="tutorial">好代码教程<b class="caret"></b></a>
      <ul class="dropdown-menu" role="menu" aria-labelledby="tutorial">
        <li role="presentation"><a rel="nofollow noopener noreferrer" href="##">CSS3</a></li>
        <li role="presentation"><a rel="nofollow noopener noreferrer" href="##">HTML5</a></li>
        <li role="presentation"><a rel="nofollow noopener noreferrer" href="##">Sass</a></li>
      </ul>
    </li>
    <li><a rel="nofollow noopener noreferrer" href="##">前端论坛</a></li>
    <li><a rel="nofollow noopener noreferrer" href="##">关于我们</a></li>
  </ul>
</div>

<h3>示例2</h3>
<ul class="nav nav-pills">
  <li class="dropdown">
    <a rel="nofollow noopener noreferrer" href="##" data-toggle="dropdown" class="dropdown-toggle" role="button" id="tutorial">好代码教程<b class="caret"></b></a>
    <ul class="dropdown-menu" role="menu" aria-labelledby="tutorial">
      <li role="presentation"><a rel="nofollow noopener noreferrer" href="##">CSS3</a></li>
      <li role="presentation"><a rel="nofollow noopener noreferrer" href="##">HTML5</a></li>
      <li role="presentation"><a rel="nofollow noopener noreferrer" href="##">Sass</a></li>
    </ul>
  </li>
  <li class="active"><a rel="nofollow noopener noreferrer" href="##">前端论坛</a></li>
  <li><a rel="nofollow noopener noreferrer" href="##">关于我们</a></li>
</ul>
<script src="http://libs.baidu.com/jquery/1.9.0/jquery.js"></script>
<script src="http://cdn.bootcss.com/bootstrap/2.3.1/js/bootstrap-dropdown.js"></script>

下拉菜单–属性声明式方法（一）

☑ 被点击的菜单项链接或按钮需要添加自定义属性 data-toggle=”dropdown”
实现下拉菜单原理：

Dropdown插件加载时，对所有带 有“data-toggle=dropdown”样式的元素绑定了事件，用户单击带有“data-toggle=dropdown”样式的链接或按钮时， 会触发JavaScript事件代码。当用户点击带有“data-toggle=dropdown”样式的链接或按钮时，下拉菜单的父容器（上面的示例是 “<li class="dropdown">”）会添加一个open类名，此时下拉菜单显示；再次单击时，JavaScript会删除刚添加的open类 名，此时下拉菜单将隐藏。

下接菜单结构:

<div class="dropdown">
  <a data-toggle="dropdown" rel="nofollow noopener noreferrer" href="#">下拉菜单触发器</a>
  <ul class="dropdown-menu" role="menu" aria-labelledby="dLabel"> ... </ul>
</div>

如果触发下拉菜单的元素是一个链接元素，为了避免点击链接，页面跳到顶部，可以使用data-target="#"来替代rel="nofollow noopener noreferrer" href="#"

<div class="dropdown">
  <a id="dLabel" role="button" data-toggle="dropdown" data-target="#" rel="nofollow noopener noreferrer" href="/page.html"> Dropdown <span class="caret"></span></a>
  <ul class="dropdown-menu" role="menu" aria-labelledby="dLabel"> ... </ul>
</div>


<ul class="nav nav-pills">
  <li><a rel="nofollow noopener noreferrer" href="##">好代码教程</a></li>
  <li class="active"><a rel="nofollow noopener noreferrer" href="##">前端论坛</a></li>
  <li class="dropdown">
    <a rel="nofollow noopener noreferrer" href="##" data-toggle="dropdown" class="dropdown-toggle">关于我们</a>   

     <ul class="dropdown-menu" role="menu" aria-labelledby="tutorial">
        <li role="presentation"><a rel="nofollow noopener noreferrer" href="##">CSS3</a></li>
        <li role="presentation"><a rel="nofollow noopener noreferrer" href="##">HTML5</a></li>
        <li role="presentation"><a rel="nofollow noopener noreferrer" href="##">Sass</a></li>
     </ul>
  </li>
</ul>

下拉菜单–JavaScript触发方法

<ul class="nav nav-pills">
  <li class="dropdown">
    <a rel="nofollow noopener noreferrer" href="##" class="dropdown-toggle" role="button" id="tutorial">好代码教程<b class="caret"></b></a>
    <ul class="dropdown-menu" role="menu" aria-labelledby="tutorial">
      <li role="presentation"><a rel="nofollow noopener noreferrer" href="##">CSS3</a></li>
      <li role="presentation"><a rel="nofollow noopener noreferrer" href="##">HTML5</a></li>
      <li role="presentation"><a rel="nofollow noopener noreferrer" href="##">Sass</a></li>
    </ul>
  </li>
  <li class="active"><a rel="nofollow noopener noreferrer" href="##">前端论坛</a></li>
  <li><a rel="nofollow noopener noreferrer" href="##">关于我们</a></li>
</ul>

<script src="http://libs.baidu.com/jquery/1.9.0/jquery.js"></script>
<script src="http://maxcdn.bootstrapcdn.com/bootstrap/3.2.0/js/bootstrap.min.js"></script>

<script>
  $(function(){
  $(".dropdown-toggle").dropdown();
})  
</script>

//显示下拉菜单：
$(function(){
  $(".dropdown-toggle").dropdown("toggle");
})

以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持。