案例：jQuery案例     状态：可编辑再运行    进入竖版
 运行结果　
​x
 
1
<!DOCTYPE html>
2
<html>
3
<head>
4
  <style>
5
  div { width:60px; height:60px; margin:10px; float:left;
6
        border:2px solid blue; }
7
  .blue { background:blue; }
8
  </style>
9
  <script type="text/javascript" src="/js/jquery.js"></script>
10
</head>
11
​
12
<body>
13
<ul>
14
  <li>list item 1</li>
15
  <li>list item 2</li>
16
  <li>list item 3</li>
17
  <li>list item 4</li>
18
  <li>list item 5</li>
19
</ul>
20
​
21
<script>$('li').eq(-2).css('background-color', 'red');</script>
22
</body>
23
</html>
24
​