2-5 滚动监控器
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滚动监控器

插件源文件：scrollspy.js

（官方发布引用地址：http://cdn.bootcss.com/bootstrap/2.3.1/js/bootstrap-scrollspy.js）

滚动监控器是Bootstrap提供的非常实用的JavaScript插件，被广泛应用到Web开发中。其表现形式是：

1、当用户鼠标滚动时，滚动条的位置会自动更新导航条中相应的导航项。如Bootstrap官网提供的示例：

（右侧结果窗口单击全屏按钮查看效果）

2、用户拖动滚动条，当滚动到@mdo时，上面的@mdo导航项就会高亮显示：

这是因为该插件可以自动检测滚动条到达哪个位置，然后在需要高亮的菜单元素上加了一个“active”样式。

任务

我来试试：在右侧结果窗口体验一下scrollspy的作用。

index.html 
  1. <!DOCTYPE HTML>
  2. <html>
  3. <head>
  4. <meta http-equiv="Content-Type" content="text/html; charset=utf-8">
  5. <title>下拉菜单--属性声明式方法（一）</title>
  6. <link rel="stylesheet" href="http://maxcdn.bootstrapcdn.com/bootstrap/3.2.0/css/bootstrap.min.css">
  7. <style>
  8. .scrollspy-example{
  9.     height:500px;
  10.     font-size:20px;
  11.     overflow:auto;
  12. }
  13. </style>
  14. </head>
  15. <body>
  16. <div class="bs-docs-section">
  17.   <h1 class="page-header" id="scrollspy">ScrollSpy <small>scrollspy.js</small></h1>
  18.   <h2 id="scrollspy-examples">Example in navbar</h2>
  19.   <p>The ScrollSpy plugin is for automatically updating nav targets based on scroll position. Scroll the area below the navbar and watch the active class change. The dropdown sub items will be highlighted as well.</p>
  20.   <div class="bs-example">
  21.     <nav role="navigation" class="navbar navbar-default navbar-static" id="navbar-example2">
  22.       <div class="container-fluid">
  23.         <div class="navbar-header">
  24.           <button data-target=".bs-example-js-navbar-scrollspy" data-toggle="collapse" type="button" class="navbar-toggle collapsed">
  25.             <span class="sr-only">Toggle navigation</span>
  26.             <span class="icon-bar"></span>
  27.             <span class="icon-bar"></span>
  28.             <span class="icon-bar"></span>
  29.           </button>
  30.           <a href="#" class="navbar-brand">Project Name</a>
  31.         </div>
  32.         <div class="collapse navbar-collapse bs-example-js-navbar-scrollspy">
  33.           <ul class="nav navbar-nav">
  34.             <li><a href="#fat">@fat</a></li>
  35.             <li><a href="#mdo">@mdo</a></li>
  36.             <li class="dropdown">
  37.               <a aria-expanded="false" role="button" data-toggle="dropdown" class="dropdown-toggle" id="navbarDrop1" href="#">Dropdown <span class="caret"></span></a>
  38.               <ul aria-labelledby="navbarDrop1" role="menu" class="dropdown-menu">
  39.                 <li><a tabindex="-1" href="#one">one</a></li>
  40.                 <li><a tabindex="-1" href="#two">two</a></li>
  41.                 <li class="divider"></li>
  42.                 <li><a tabindex="-1" href="#three">three</a></li>
  43.               </ul>
  44.             </li>
  45.           </ul>
  46.         </div>
  47.       </div>
  48.     </nav>
  49.     <div class="scrollspy-example" data-offset="0" data-target="#navbar-example2" data-spy="scroll">
  50.       <h4 id="fat">@fat</h4>
  51.       <p>Ad leggings keytar, brunch id art party dolor labore. Pitchfork yr enim lo-fi before they sold out qui. Tumblr farm-to-table bicycle rights whatever. Anim keffiyeh carles cardigan. Velit seitan mcsweeney's photo booth 3 wolf moon irure. Cosby sweater lomo jean shorts, williamsburg hoodie minim qui you probably haven't heard of them et cardigan trust fund culpa biodiesel wes anderson aesthetic. Nihil tattooed accusamus, cred irony biodiesel keffiyeh artisan ullamco consequat.</p>
  52.       <h4 id="mdo">@mdo</h4>
  53.       <p>Veniam marfa mustache skateboard, adipisicing fugiat velit pitchfork beard. Freegan beard aliqua cupidatat mcsweeney's vero. Cupidatat four loko nisi, ea helvetica nulla carles. Tattooed cosby sweater food truck, mcsweeney's quis non freegan vinyl. Lo-fi wes anderson +1 sartorial. Carles non aesthetic exercitation quis gentrify. Brooklyn adipisicing craft beer vice keytar deserunt.</p>
  54.       <h4 id="one">one</h4>
  55.       <p>Occaecat commodo aliqua delectus. Fap craft beer deserunt skateboard ea. Lomo bicycle rights adipisicing banh mi, velit ea sunt next level locavore single-origin coffee in magna veniam. High life id vinyl, echo park consequat quis aliquip banh mi pitchfork. Vero VHS est adipisicing. Consectetur nisi DIY minim messenger bag. Cred ex in, sustainable delectus consectetur fanny pack iphone.</p>
  56.       <h4 id="two">two</h4>
  57.       <p>In incididunt echo park, officia deserunt mcsweeney's proident master cleanse thundercats sapiente veniam. Excepteur VHS elit, proident shoreditch +1 biodiesel laborum craft beer. Single-origin coffee wayfarers irure four loko, cupidatat terry richardson master cleanse. Assumenda you probably haven't heard of them art party fanny pack, tattooed nulla cardigan tempor ad. Proident wolf nesciunt sartorial keffiyeh eu banh mi sustainable. Elit wolf voluptate, lo-fi ea portland before they sold out four loko. Locavore enim nostrud mlkshk brooklyn nesciunt.</p>
  58.       <h4 id="three">three</h4>
  59.       <p>Ad leggings keytar, brunch id art party dolor labore. Pitchfork yr enim lo-fi before they sold out qui. Tumblr farm-to-table bicycle rights whatever. Anim keffiyeh carles cardigan. Velit seitan mcsweeney's photo booth 3 wolf moon irure. Cosby sweater lomo jean shorts, williamsburg hoodie minim qui you probably haven't heard of them et cardigan trust fund culpa biodiesel wes anderson aesthetic. Nihil tattooed accusamus, cred irony biodiesel keffiyeh artisan ullamco consequat.</p>
  60.       <p>Keytar twee blog, culpa messenger bag marfa whatever delectus food truck. Sapiente synth id assumenda. Locavore sed helvetica cliche irony, thundercats you probably haven't heard of them consequat hoodie gluten-free lo-fi fap aliquip. Labore elit placeat before they sold out, terry richardson proident brunch nesciunt quis cosby sweater pariatur keffiyeh ut helvetica artisan. Cardigan craft beer seitan readymade velit. VHS chambray laboris tempor veniam. Anim mollit minim commodo ullamco thundercats.
  61.       </p>
  62.  
  63.     </div>
  64.   </div><!-- /example -->
  65.  
  66.  
  67. </div>
  68. <script src="http://libs.baidu.com/jquery/1.9.0/jquery.js"></script>
  69. <script src="http://cdn.bootcss.com/bootstrap/2.3.1/js/bootstrap-dropdown.js"></script>
  70. <script src="http://cdn.bootcss.com/bootstrap/2.3.1/js/bootstrap-scrollspy.js"></script>
  71.  
  72. </body>
  73. </html>
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