JS+CSS制作的动态二级下拉导航菜单

<!doctype html> <html> <head> <meta charset="utf-8"> <title>动态二级下拉导航菜单</title> <style type="text/css"> *{margin:0;padding:0;font-style:normal;font-family:宋体;} body{text-align:center;font-size:16px;} #content{margin:0 auto;width:600px;} #content #nav{background:#006400;height:40px;margin-top:60px;} #content #nav ul{list-style:none;} #content #nav ul li{float:left;width:100px;line-height:40px;position:relative;} #nav div{width:100px;position:absolute;left:0px;padding-bottom:0px;background:#006400;float:left;height:0;overflow:hidden;} #content #nav li .a{text-decoration:none;color: #FF0;line-height:40px;display:block;border-right:1px solid #009800;} #nav div a{text-decoration:none;color: #FF0;line-height:26px;display:block;} #nav div a:hover{background:#005400;} </style> </head> <body> <div id="content"> <div id="nav"> <ul id="supnav"> <li><a href="http://www.125jz.com/" class="a">网页制作</a> <div> <a href="#">网页制作</a> <a href="#">网页制作</a> <a href="#">网页制作</a> <a href="#">网页制作</a> <a href="#">网页制作</a> </div> </li> <li><a href="http://www.125jz.com/resources/effects" class="a">网页特效</a> <div> <a href="#">网页制作</a> <a href="#">网页制作</a> </div> </li> <li><a href="#" class="a">网页制作</a> <div> <a href="#">网页制作</a> <a href="#">网页制作</a> <a href="#">网页制作</a> <a href="#">网页制作</a> </div> </li> <li><a href="#" class="a">网页制作</a> <div> </div> </li> <li><a href="http://www.125jz.com/design/coolsite" class="a">酷站欣赏</a> <div> </div> </li> <li><a href="http://www.125jz.com/design/images" class="a">设计素材</a> <div> <a href="#">网页制作</a> <a href="#">网页制作</a> <a href="#">网页制作</a> <a href="#">网页制作</a> </div> </li> </ul> </div> </div> <script type="text/javascript"> var supnav=document.getElementById("supnav"); var nav=document.getElementById("nav"); var btns=document.getElementsByTagName("li"); var subnavs=nav.getElementsByTagName("div"); var paddingbottom=20; var defaultHeight=0; function drop(obj,ivalue){ var a=obj.offsetHeight; var speed=(ivalue-obj.offsetHeight)/8; a+=Math.floor(speed); obj.style.height=a+"px"; } window.onload=function(){ for(var i=0;i<btns.length;i++){ btns[i].index=i; btns[i].onmouseover=function(){ var osubnav=subnavs[this.index]; var sublinks=osubnav.getElementsByTagName("a"); if(osubnav.firstChild.tagName==undefined){ var itarheight=parseInt(osubnav.childNodes[1].offsetHeight)*sublinks.length+paddingbottom; } else{ var itarheight=parseInt(osubnav.firstChild.offsetHeight)*sublinks.length+paddingbottom;} clearInterval(this.itimer); this.itimer=setInterval(function(){drop(osubnav,itarheight);},30); } btns[i].onmouseout=function(){ var osubnav=subnavs[this.index]; clearInterval(this.itimer); this.itimer=setInterval(function(){drop(osubnav,defaultHeight);},30); } } } </script> </body> </html>

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