Bootstrap官网用法:http://getbootstrap.com/javascript/#dropdowns
原文如下：
data-toggle="dropdown" still required
Regardless of whether you call your dropdown via JavaScript or instead use the data-api, data-toggle="dropdown" is always required to be present on the dropdown's trigger element.
童鞋，谢谢分享。不过笔记最好放在笔记那边。