Bootstrap3下拉菜单的实现

<div class="dropdown">
 <button id="dlabel" type="button" data-toggle="dropdown" aria-haspopup="true" aria-expanded="false">
  dropdown trigger
  <span class="caret"></span>
 </button>
 <ul class="dropdown-menu" aria-labelledby="dlabel">
  ...
 </ul>
</div>

$('.dropdown-toggle').dropdown()

$().dropdown('toggle')

$('#mydropdown').on('show.bs.dropdown', function () {
 // do something…
})