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> <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="#">查字典教程网</a></li> <li><a href="#">Navigation Item 2</a></li> <li><a href="#">Navigation Item 3</a></li> <li><a href="#">Navigation Item 4</a></li> <li><a href="#">Navigation Item 5</a></li> </ul> </dd> </dl> <dl> <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="#">Navigation Item 1</a></li> <li><a href="#">Navigation Item 2</a></li> <li><a href="#">Navigation Item 3</a></li> <li><a href="#">默认主页</a></li> <li><a href="#">Navigation Item 5</a></li> </ul> </dd> </dl> <dl> <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="#">Navigation Item 1</a></li> <li><a href="#">Navigation Item 2</a></li> <li><a href="#">Navigation Item 3</a></li> <li><a href="#">Navigation Item 4</a></li> <li><a href="#">Navigation Item 5</a></li> </ul> </dd> </dl> <dl> <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="#">默认主页</a></li> <li><a href="#">Navigation Item 2</a></li> <li><a href="#">Navigation Item 3</a></li> <li><a href="#">Navigation Item 4</a></li> <li><a href="#">Navigation Item 5</a></li> </ul> </dd> </dl> <dl> <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="#">Navigation Item 1</a></li> <li><a href="#">默认主页</a></li> <li><a href="#">Navigation Item 3</a></li> <li><a href="#">Navigation Item 4</a></li> <li><a href="#">Navigation Item 5</a></li> </ul> </dd> </dl> <dl> <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="#">Navigation Item 1</a></li> <li><a href="#">Navigation Item 2</a></li> <li><a href="#">Navigation Item 3</a></li> <li><a href="#">Navigation Item 4</a></li> <li><a href="#">Navigation Item 5</a></li> </ul> </dd> </dl> <dl> <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="#">Navigat</a></li> <li><a href="#">Naviga</a></li> <li><a href="#">Navigati</a></li> <li><a href="#">Navigat</a></li> <li><a href="#">Navigatio</a></li> </ul> </dd> </dl> <div> </div> </body> </html>
希望本文所述对大家的JavaScript程序设计有所帮助。
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