功能：实现点击时下拉框显示
插件：dropdown.js
要点：dropdown功能往往用在导航栏、导航条上，用作标题显示。dropdown与<ul><li>标签搭配用。
以data-toggle作被点击者，以ul class="dropdown-menu"作展开显示，对被点击者、展开者作一个整体li class="dropdown"包围
<!DOCTYPE html> <html lang=""> <head> <meta charset="utf-8"> <meta http-equiv="X-UA-Compatible" content="IE=edge"> <meta name="viewport" content="width=device-width, initial-scale=1"> <title>Title Page</title> <!-- Bootstrap CSS --> <!-- jquery 与 boostrap 的先后加载也会影响其下拉菜单的显示，看来要用requireJs 解决依赖关系了 --> <script src="../bootstrap-3.3.5-dist/js/bootstrap.min.js"></script> <script src="../extlib/jquery-1.11.1.min.js" type="text/javascript" charset="utf-8"></script> <!-- Local bootstrap CSS & JS --> <script src="../bootstrap-3.3.5-dist/js/collapse.js"></script> <script src="../bootstrap-3.3.5-dist/js/scrollspy.js"></script> <script src="../bootstrap-3.3.5-dist/js/transition.js"></script> <script src="../bootstrap-3.3.5-dist/js/dropdown.js"></script> <script src="../bootstrap-3.3.5-dist/js/alert.js"></script> <link rel="stylesheet" media="screen" href="../bootstrap-3.3.5-dist/css/bootstrap.min.css"> <!-- HTML5 Shim and Respond.js IE8 support of HTML5 elements and media queries --> <!-- WARNING: Respond.js doesn't work if you view the page via file:// --> <!--[if lt IE 9]> <script src="https://oss.maxcdn.com/libs/html5shiv/3.7.0/html5shiv.js"></script> <script src="https://oss.maxcdn.com/libs/respond.js/1.4.2/respond.min.js"></script> <![endif]--> </head> <body> <h1 class="text-center">Hello World</h1> <!-- 显示下拉框，一般与nav navbar-nav ul li结合，关键词：dropdown dropdown-toggle data-toggle="dropdown" drop-menu --> <!-- boostrap 限制了灵活性 --> <nav class="navbar navbar-default navbar-fixed-top" role="navigation"> <a class="navbar-brand" href="#">Title</a> <ul class="nav navbar-nav"> <li class="active"> <a href="#">Home</a> </li> <li> <a href="#">Link</a> </li> </ul> <div class="collapse navbar-collapse js-navbar-scrollspy"> <ul class="nav navbar-nav"> <li><a href="">kkk</a></li> <li class="dropdown"> <a href="#" class="dropdown-toggle" data-toggle="dropdown">dropdown</a> <ul class="dropdown-menu"> <li><a href="" tabindex="-1">aaaaaaa</a></li> <li><a href="" tabindex="-1">bbbbbbbbbbb</a></li> </ul> </li> </ul> </div> </nav> </body> </html>