JavaScript简单下拉菜单实例代码

本文实例讲述了JavaScript简单下拉菜单实例代码。分享给大家供大家参考。具体如下：

这是一款JavaScript实现的下拉菜单演示代码，带渐变效果的CSS+jQuery菜单，向下滑出型的菜单，最高支持两级，网上常见到的一种菜单风格，希望大家喜欢哦。

运行效果截图如下：

在线演示地址如下：

http://demo.jb51.net/js/2015/js-simple-xlcd-down-menu-codes/

具体代码如下：

<!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=UTF-8">
<title>JavaScript下拉菜单演示代码</title>
<style type="text/css">
body {margin:25px; font:12px Verdana, Arial, Helvetica}
* {padding:0; margin:0}
.dropdown {float:left; padding-right:0px}
.dropdown dt {width:80px; border:2px solid #9ac1c9; padding:8px; font-weight:bold; cursor:pointer; background:url()}
.dropdown dt:hover {background:url()}
.dropdown dd {position:absolute; overflow:hidden; width:100px; display:none; background:#fff; z-index:200; opacity:0}
.dropdown ul {width:100px; border:2px solid #9ac1c9; list-style:none; border-top:none}
.dropdown li {display:inline}
.dropdown a, .dropdown a:active, .dropdown a:visited {display:block; padding:5px; color:#333; text-decoration:none; background:#eaf0f2; width:194px}
.dropdown a:hover {background:#d9e1e4; color:#000}
.dropdown .underline {border-bottom:1px solid #b9d6dc}
</style>
<script language="javascript">
var DDSPEED = 10;
var DDTIMER = 15;
function ddMenu(id,d){
 var h = document.getElementById(id + '-ddheader');
 var c = document.getElementById(id + '-ddcontent');
 clearInterval(c.timer);
 if(d == 1){
  clearTimeout(h.timer);
  if(c.maxh && c.maxh <= c.offsetHeight){return}
  else if(!c.maxh){
   c.style.display = 'block';
   c.style.height = 'auto';
   c.maxh = c.offsetHeight;
   c.style.height = '0px';
  }
  c.timer = setInterval(function(){ddSlide(c,1)},DDTIMER);
 }else{
  h.timer = setTimeout(function(){ddCollapse(c)},50);
 }
}
// collapse the menu //
function ddCollapse(c){
 c.timer = setInterval(function(){ddSlide(c,-1)},DDTIMER);
}
function cancelHide(id){
 var h = document.getElementById(id + '-ddheader');
 var c = document.getElementById(id + '-ddcontent');
 clearTimeout(h.timer);
 clearInterval(c.timer);
 if(c.offsetHeight < c.maxh){
  c.timer = setInterval(function(){ddSlide(c,1)},DDTIMER);
 }
}
function ddSlide(c,d){
 var currh = c.offsetHeight;
 var dist;
 if(d == 1){
  dist = (Math.round((c.maxh - currh) / DDSPEED));
 }else{
  dist = (Math.round(currh / DDSPEED));
 }
 if(dist <= 1 && d == 1){
  dist = 1;
 }
 c.style.height = currh + (dist * d) + 'px';
 c.style.opacity = currh / c.maxh;
 c.style.filter = 'alpha(opacity=' + (currh * 100 / c.maxh) + ')';
   if((currh < 2 && d != 1) || (currh > (c.maxh - 2) && d == 1)){
   clearInterval(c.timer);
   }
   }
   </script>
   </head>
   <body>
   <br><br>
   <dl class="dropdown">
   <dt id="one-ddheader" onmouseover="ddMenu('one',1)" onmouseout="ddMenu('one',-1)">One</dt>
   <dd id="one-ddcontent" onmouseover="cancelHide('one')" onmouseout="ddMenu('one',-1)">
   <ul>
   <li><a href="#" class="underline">我们</a></li>
   <li><a href="#" class="underline">Navigation Item 2</a></li>
   <li><a href="#" class="underline">Navigation Item 3</a></li>
   <li><a href="#" class="underline">Navigation Item 4</a></li>
   <li><a href="#">Navigation Item 5</a></li>
 </ul>
 </dd>
 </dl>
 <dl class="dropdown">
 <dt id="two-ddheader" onmouseover="ddMenu('two',1)" onmouseout="ddMenu('two',-1)">Two</dt>
 <dd id="two-ddcontent" onmouseover="cancelHide('two')" onmouseout="ddMenu('two',-1)">
 <ul>
 <li><a href="#" class="underline">Navigation Item 1</a></li>
 <li><a href="#" class="underline">Navigation Item 2</a></li>
 <li><a href="#" class="underline">Navigation Item 3</a></li>
 <li><a href="#" class="underline">默认主页</a></li>
 <li><a href="#">Navigation Item 5</a></li>
 </ul>
 </dd>
 </dl>
 <dl class="dropdown">
 <dt id="three-ddheader" onmouseover="ddMenu('three',1)" onmouseout="ddMenu('three',-1)">Two</dt>
 <dd id="three-ddcontent" onmouseover="cancelHide('three')" onmouseout="ddMenu('three',-1)">
 <ul>
 <li><a href="#" class="underline">Navigation Item 1</a></li>
 <li><a href="#" class="underline">Navigation Item 2</a></li>
 <li><a href="#" class="underline">Navigation Item 3</a></li>
 <li><a href="#" class="underline">Navigation Item 4</a></li>
 <li><a href="#">Navigation Item 5</a></li>
 </ul>
 </dd>
 </dl>
 <dl class="dropdown">
 <dt id="four-ddheader" onmouseover="ddMenu('four',1)" onmouseout="ddMenu('four',-1)">Two</dt>
 <dd id="four-ddcontent" onmouseover="cancelHide('four')" onmouseout="ddMenu('four',-1)">
 <ul>
 <li><a href="#" class="underline">默认主页</a></li>
 <li><a href="#" class="underline">Navigation Item 2</a></li>
 <li><a href="#" class="underline">Navigation Item 3</a></li>
 <li><a href="#" class="underline">Navigation Item 4</a></li>
 <li><a href="#">Navigation Item 5</a></li>
 </ul>
 </dd>
 </dl>
 <dl class="dropdown">
 <dt id="fir-ddheader" onmouseover="ddMenu('fir',1)" onmouseout="ddMenu('fir',-1)">Two</dt>
 <dd id="fir-ddcontent" onmouseover="cancelHide('fir')" onmouseout="ddMenu('fir',-1)">
 <ul>
 <li><a href="#" class="underline">Navigation Item 1</a></li>
 <li><a href="#" class="underline">默认主页</a></li>
 <li><a href="#" class="underline">Navigation Item 3</a></li>
 <li><a href="#" class="underline">Navigation Item 4</a></li>
 <li><a href="#">Navigation Item 5</a></li>
 </ul>
 </dd>
 </dl>
 <dl class="dropdown">
 <dt id="six-ddheader" onmouseover="ddMenu('six',1)" onmouseout="ddMenu('six',-1)">Two</dt>
 <dd id="six-ddcontent" onmouseover="cancelHide('six')" onmouseout="ddMenu('six',-1)">
 <ul>
 <li><a href="#" class="underline">Navigation Item 1</a></li>
 <li><a href="#" class="underline">Navigation Item 2</a></li>
 <li><a href="#" class="underline">Navigation Item 3</a></li>
 <li><a href="#" class="underline">Navigation Item 4</a></li>
 <li><a href="#">Navigation Item 5</a></li>
 </ul>
 </dd>
 </dl>
 <dl class="dropdown">
 <dt id="seven-ddheader" onmouseover="ddMenu('seven',1)" onmouseout="ddMenu('seven',-1)">Two</dt>
 <dd id="seven-ddcontent" onmouseover="cancelHide('seven')" onmouseout="ddMenu('seven',-1)">
 <ul>
 <li><a href="#" class="underline">Navigat</a></li>
 <li><a href="#" class="underline">Naviga</a></li>
 <li><a href="#" class="underline">Navigati</a></li>
 <li><a href="#" class="underline">Navigat</a></li>
 <li><a href="#">Navigatio</a></li>
 </ul>
 </dd>
 </dl>
 <div style="clear:both">
 </div>
</body>
</html>

希望本文所述对大家的JavaScript程序设计有所帮助。