JavaScript implements display and hiding of drop-down menu

JavaScript implements display and hiding of drop-down menu_javascript skills

WBOY

Release： 2016-05-16 15:21:51

Original

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In this article, we will use JavaScript script to display and hide the drop-down menu. The knowledge we need to use JavaScript methods to implement is:
1) JS events: onmouseover mouse passing event and onmouseout mouse leaving event.
2) JS basic syntax: Use the function keyword to define functions.
3) DOM programming: getElementsByTagName() method.
Then the next step is our production process:
1) Hide the secondary menu: Set the CSS style to hide the secondary menu.
2) Write the showsub() function to display the submenu: use getElementsByTagName to obtain the secondary menu items; set the secondary menu display through style.display.
3) Write the hidesub() function of the hidden submenu: use getElementsByTagName to obtain the secondary menu items; set the secondary menu to be hidden through style.display.
4) Add mouse events: Add mouse events to the first-level menu with a second-level menu, and call the showsub()/hidesub() function to realize the display and hiding of the second-level menu when the mouse passes through the first-level menu.
5) Do browser compatibility testing, at least five browsers. IE7,8,9, Firefox, Google, 2345 browser, etc.

Rendering:

HTML code:

<span style="font-size:18px;"><!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> 
<html xmlns="http://www.w3.org/1999/xhtml"> 
<head> 
<meta http-equiv="Content-Type" content="text/html; charset=gb2312" /> 
<title>下拉菜单</title> 
<!--引入的外部CSS样式文件--> 
<link rel="stylesheet" type="text/css" href="style.css" /> 
<!--引入的外部JS脚本文件--> 
<script type="text/javascript" src="script.js"></script> 
</head> 
 
<body> 
<div id="nav" class="nav"> 
 <ul> 
  <li><a href="#">网站首页</a></li> 
  <li onmouseover="showsub(this)" onmouseout="hidesub(this)"><a href="#">课程大厅</a> 
  <ul> 
   <li><a href="#">JavaScript</a></li> 
   <li><a href="#">jQuery</a></li> 
   <li><a href="#">Ajax</a></li> 
  </ul> 
  </li> 
  <li onmouseover="showsub(this)" onmouseout="hidesub(this)"><a href="#">学习中心</a> 
  <ul> 
   <li><a href="#">视频学习</a></li> 
   <li><a href="#">案例学习</a></li> 
   <li><a href="#">交流平台</a></li> 
  </ul> 
  </li> 
  <li><a href="#">经典案例</a></li> 
  <li><a href="#">关于我们</a></li> 
 </ul> 
</div> 
</body> 
</html> 
</span>

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External CSS style sheet style.css file code:

<span style="font-size:18px;">/*CSS全局设置*/ 
*{ 
 margin:0; 
 padding:0; 
} 
.nav{ 
 background-color:#EEEEEE; 
 height:40px; 
 width:450px; 
 margin:0 auto; 
} 
ul{ 
 list-style:none; 
} 
ul li{ 
 float:left; 
 line-height:40px; 
 text-align:center; 
} 
a{ 
 text-decoration:none; 
 color:#000000; 
 display:block; 
 width:90px; 
 height:40px; 
} 
a:hover{ 
 background-color:#666666; 
 color:#FFFFFF; 
} 
ul li ul li{ 
 float:none; 
 background-color:#EEEEEE; 
} 
ul li ul{ 
 display:none; 
} 
/*为了兼容IE7设置的CSS样式，但是又必须写在a:hover前面*/ 
ul li ul li a:link,ul li ul li a:visited{ 
 background-color:#EEEEEE; 
} 
ul li ul li a:hover{ 
 background-color:#009933; 
} 
</span>

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External JS script script.js file code:

<span style="font-size:18px;">function showsub(li){ 
 var submenu=li.getElementsByTagName("ul")[0]; 
 submenu.style.display="block"; 
} 
function hidesub(li){ 
 var submenu=li.getElementsByTagName("ul")[0]; 
 submenu.style.display="none"; 
}</span>

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The above is the entire content of this article. I hope it will be helpful to everyone’s study and achieve the drop-down menu effect.