jquery实现⼆级导航下拉菜单效果实例
⼤家都知道jQuery是⼀个框架，它对JS进⾏了封装，使其更⽅便使⽤。前⾯两篇博⽂分别是⽤CSS样式和JS实现的，那么这篇就⽤jQuery 来实现⼆级下拉式菜单。
使⽤JQuery实现需要⽤到的知识有：
1. 1)使⽤$(function(){...})获取到想要作⽤的HTML元素。
2. 2)通过使⽤children()⽅法寻⼦元素。
3. 3)通过使⽤show()⽅法来显⽰HTML元素。
4. 4)通过使⽤hide()⽅法来隐藏HTML元素。
5. 5)jQuery库引⽤⽅法:
第⼀种⽅法：将jQuery库下载到电脑上，然后引⽤，我下载的是jquery-1.7.1.min.js这个版本。
例如：
1. <script type="text/javascript" src="jquery/jquery-1.7.1.min.js"></script>
第⼆种⽅法：直接引⽤在线服务器上的jQuery库⽂件，⽐如⾕歌服务器jQuery库，百度服务器jQuery库等。
例如：引⽤百度服务器上的jQuery库⽂件
1. <script type="text/javascript" src="jquery/1.9.0/jquery.js"></script>
接下来看看制作的流程：
1. 1、调⽤jQuery库：编写代码，引⽤jquery库。由于⾕歌已退出⼤陆，建议使⽤百度服务器的jQuery库。
2. 注意: 百度服务器的jQuery库地址:libs.baidu/jquery/1.9.0/jquery.js
3. 2 、编写显⽰⼦菜单函数，使⽤$，并通过class名获取⼀级菜单li，过children()到li的孩⼦元素ul，使⽤show()⽅法，显⽰⼆级菜单。
4. 3、编写隐藏⼦菜单函数，使⽤$，并通过class名获取⼀级菜单li，过children()到li的孩⼦元素ul，使⽤hide()⽅法, 隐藏⼆级菜单。
5. 4、做浏览器兼容性测试，⾄少五个浏览器。IE7,8,9，⽕狐，⾕歌，2345浏览器等。
先来看看效果图：
最后我们来看看代码的情况，和前⾯的区别不⼤：
HTML代码：
1. <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "/TR/xhtml1/DTD/xhtml1-
transitional.dtd">
2.
3. <html
4. xmlns="/1999/xhtml">
5.
6. <head>
7.
9. http-equiv="Content-Type"
10. content="text/html; charset=gb2312" />
11.
12. <title>下拉菜单</title>
13.
14. <link
15. rel="stylesheet"
16. type="text/css"
17. href="style.css" rel="external nofollow"
18. />
19.
20. <!--引⽤百度服务器的jQuery库-->
21.
22. <script
23. src="libs.baidu/jquery/1.9.0/jquery.js"></script>
24.
25. <script
26. type="text/javascript"
27. src="script.js"></script>
28.
29. </head>
30.
31.
32.
33. <body>
34.
35. <div
36. id="nav"
37. class="nav">
38.
39.  <ul>
40.
41.    <li><a
42. href="#" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external
nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" >⽹站⾸页</a></li>
43.
44.    <li
45. class="navmenu"><a
46. href="#" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external
nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" >课程⼤厅</a>
47.
49.
50.      <li><a
51. href="#" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external
nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" >JavaScript</a></li>
52.
53.      <li><a
54. href="#" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external
nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" >jQuery</a></li>
55.
56.      <li><a
57. href="#" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external
nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" >Ajax</a></li>
58.
59.    </ul>
60.
61.    </li>
62.
63.    <li
64. class="navmenu"><a
65. href="#" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofoll
ow" rel="external
nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" >学习中⼼</a>
66.
67.    <ul>
68.
69.      <li><a
70. href="#" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external
nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" >视频学习</a></li>
71.
72.      <li><a
73. href="#" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external
nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" >案例学习</a></li>
74.
75.      <li><a
76. href="#" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external
nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" >交流平台</a></li>
77.
78.    </ul>
79.
80.    </li>
81.
82.    <li><a
83. href="#" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external
nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" >经典案例</a></li>
84.
85.    <li><a
86. href="#" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external
nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" >关于我们</a></li>
87.
88.  </ul>
html下拉菜单的制作方法89.
90. </div>
91.
92. </body>
93.
94. </html>
CSS样式表外部style.css⽂件代码：
1. /*CSS全局设置*/
2.
3. *{
4.
5.  margin:0;
6.
7.  padding:0;
8.
9. }
10.
11. .nav{
12.
13.  background-color:#EEEEEE;
14.
15.  height:40px;
16.
17.  width:450px;
18.
19.  margin:0
20. auto;
21.
22. }
23.
24. ul{
25.
26.  list-style:none;
27.
28. }
29.
30. ul li{
31.
32.  float:left;
33.
34.  line-height:40px;
35.
36.  text-align:center;
37.
38. }
39.
40. a{
41.
42.  text-decoration:none;
43.
44.  color:#000000;
45.
46.  display:block;
47.
48.  width:90px;
49.
50.  height:40px;
51.
52. }
53.
54. a:hover{
55.
56.  background-color:#666666;
57.
58.  color:#FFFFFF;
59.
60. }
61.
62. ul li ul li{
63.
64.  float:none;
65.
66.  background-color:#EEEEEE;

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