``` <div class="dropdown"> <button class="btn btn-default dropdown-toggle" type="button" data-toggle="dropdown"> 手机品牌 <span class="caret"></span> </button> <ul class="dropdown-menu" role="menu"> <li><a href="#">苹果</a></li> <li><a href="#">小米</a></li> <li><a href="#">魅族</a></li> </ul> </div> ``` ``` 1.给以class为dropdown的容器 <div class="dropdown"></div> 2.用btn按钮作用父菜单,定义类名dropdown-toggle，自定义属性data-toggle="dropdown" 3.下拉菜单的类名定义为dropdown-menu ```