代码简介：
js实现无限级树形下拉导航菜单，简洁实用，用到一个已封装好的JS类，有用的大家借鉴一下。
代码简介：
<title>【荐】JS封装的一个无限级的下拉树形菜单_网页代码站(www.webdm.cn)</title>
<style type="text/css">
*{ margin:0; padding:0; list-style:none;}
body { margin:20px;}
h2 { font-family:"黑体"; font-size:24px; text-align:center; line-height:32px;}
h5 { font-size:12px; text-align:center; font-weight:normal; color:#666; line-height:28px;}
#nav a { text-decoration:underline;color:#06c; font-size:14px; line-height:24px;}
#nav ul{ margin-bottom:5px;}
#nav strong{ color:#696;}
#nav.dyn li ul{ display:none;}
#nav.dyn li ul.show{ display:block;}
#nav.dyn li{ padding-left:15px;}
#nav.dyn li.parent{ background:url(http://www.webdm.cn/images/20101213/3/user_23.gif) 5px 10px no-repeat;}
#nav.dyn li.open{ background:url(http://www.webdm.cn/images/20101213/3/user_23.gif) 5px -34px no-repeat;}
</style>
<script type="text/javascript">
DOMhelp = {
debugWindowId: 'DOMhelpdebug',
init: function() {
if (!document.getElementById || !document.createTextNode) { return; }
},
lastSibling: function(node) {
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while (tempObj.nodeType != 1 && tempObj.previousSibling != null) {
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while (tempObj.nodeType != 1 && tempObj.nextSibling != null) {
tempObj = tempObj.nextSibling;
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return (tempObj.nodeType == 1) ? tempObj : false;
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setText: function(node, txt) {
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if (tempObj.nodeType == 3) { tempObj.nodeValue = txt } else { return false; }
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var tempObj = document.createElement('a');
tempObj.appendChild(document.createTextNode(txt));
tempObj.setAttribute('href', to);
return tempObj;
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createTextElm: function(elm, txt) {
var tempObj = document.createElement(elm);
tempObj.appendChild(document.createTextNode(txt));
return tempObj;
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while (tempObj.nodeType != 1 && tempObj.nextSibling != null) {
tempObj = tempObj.nextSibling;
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return tempObj.nodeType == 1 ? tempObj : false;
},
initDebug: function() {
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DOMhelp.debug = document.createElement('div');
DOMhelp.debug.setAttribute('id', DOMhelp.debugWindowId);
document.body.insertBefore(DOMhelp.debug, document.body.firstChild);
},
setDebug: function(bug) {
if (!DOMhelp.debug) { DOMhelp.initDebug(); }
DOMhelp.debug.innerHTML += bug + '\n';
},
stopDebug: function() {
if (DOMhelp.debug) {
DOMhelp.debug.parentNode.removeChild(DOMhelp.debug);
DOMhelp.debug = null;
}
},
getKey: function(e) {
if (window.event) {
var key = window.event.keyCode;
} else if (e) {
var key = e.keyCode;
}
return key;
},
/* helper methods */
getTarget: function(e) {
var target = window.event ? window.event.srcElement : e ? e.target : null;
if (!target) { return false; }
while (target.nodeType != 1 && target.nodeName.toLowerCase() != 'body') {
target = target.parentNode;
}
return target;
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e.preventDefault();
}
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return r;
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case 'swap':
o.className = !DOMhelp.cssjs('check', o, c1) ? o.className.replace(c2, c1) : o.className.replace(c1, c2);
break;
case 'add':
if (!DOMhelp.cssjs('check', o, c1)) { o.className += o.className ? ' ' + c1 : c1; }
break;
case 'remove':
var rep = o.className.match(' ' + c1) ? ' ' + c1 : c1;
o.className = o.className.replace(rep, '');
break;
case 'check':
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var temparray = o.className.split(' ');
for (var i = 0; i < temparray.length; i++) {
if (temparray[i] == c1) { found = true; }
}
return found;
break;
}
},
safariClickFix: function() {
return false;
}
}
DOMhelp.addEvent(window, 'load', DOMhelp.init, false);
</script>
<script type="text/javascript">
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sn = {
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showClass: 'show',
parentClass: 'parent',
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DOMhelp.addEvent(triggerLink, 'click', sn.changeSection, false);
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DOMhelp.cssjs('add', nested[i], sn.showClass);
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var firstList = t.parentNode.getElementsByTagName('ul')[0];
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DOMhelp.cssjs('remove', firstList, sn.showClass)
DOMhelp.cssjs('swap', t.parentNode, sn.openClass, sn.parentClass);
} else {
DOMhelp.cssjs('add', firstList, sn.showClass)
DOMhelp.cssjs('swap', t.parentNode, sn.openClass, sn.parentClass);
}
DOMhelp.cancelClick(e);
}
}
DOMhelp.addEvent(window, 'load', sn.init, false);
-->
</script>
<h2>【荐】JS封装的一个无限级的下拉树形菜单_网页代码站(www.webdm.cn)</h2>
<ul id="nav">
<li><a href="#">主页</a></li>
<li><a href="#">产品</a>
<ul>
<li><a href="#">大类别一</a>
<ul>
<li><a href="#">小类别一</a>
<ul>
<li><a href="#">次类别一</a></li>
<li><a href="#">次类别二</a></li>
</ul>
</li>
<li><a href="#">小类别二</a></li>
</ul>
</li>
<li><a href="#">大类别二</a></li>
<li><a href="#">大类别三</a>
<ul>
<li><a href="#">小类别一</a></li>
<li><a href="#">小类别二</a></li>
</ul>
</li>
</ul>
</li>
<li><a href="#">服务</a>
<ul>
<li><a href="#">大类别一</a></li>
<li><a href="#">大类别二</a></li>
<li><a href="#">大类别三</a></li>
</ul>
</li>
<li><a href="#">合作</a></li>
<li><a href="#">关于我们</a>
<ul>
<li><a href="#">大类别一</a>
<ul>
<li><a href="#">小类别一</a></li>
<li><a href="#">小类别二</a></li>
</ul>
</li>
<li><a href="#">大类别二</a>
<ul>
<li><a href="#">小类别一</a></li>
<li><a href="#">小类别二</a></li>
</ul>
</li>
<li><a href="#">大类别三</a>
<ul>
<li><a href="#">小类别一</a></li>
<li><a href="#">小类别二</a></li>
</ul>
</li>
<li><a href="#">大类别四</a></li>
</ul>
</li>
<li><a href="#">联系我们</a>
<ul>
<li><a href="#">大类别一</a></li>
<li><a href="#">大类别二</a></li>
</ul>
</li>
</ul>
<br />
<p>
<a href="http://www.webdm.cn">网页代码站</a> - 最专业的网页代码下载网站 - 致力为中国站长提供有质量的网页代码！</p>
代码来自：http://www.webdm.cn/webcode/790e8b32-a44e-499f-a5a2-12c4321b356e.html
<style type="text/css">
*{ margin:0; padding:0; list-style:none;}
body { margin:20px;}
h2 { font-family:"黑体"; font-size:24px; text-align:center; line-height:32px;}
h5 { font-size:12px; text-align:center; font-weight:normal; color:#666; line-height:28px;}
#nav a { text-decoration:underline;color:#06c; font-size:14px; line-height:24px;}
#nav ul{ margin-bottom:5px;}
#nav strong{ color:#696;}
#nav.dyn li ul{ display:none;}
#nav.dyn li ul.show{ display:block;}
#nav.dyn li{ padding-left:15px;}
#nav.dyn li.parent{ background:url(http://www.webdm.cn/images/20101213/3/user_23.gif) 5px 10px no-repeat;}
#nav.dyn li.open{ background:url(http://www.webdm.cn/images/20101213/3/user_23.gif) 5px -34px no-repeat;}
</style>
<script type="text/javascript">
DOMhelp = {
debugWindowId: 'DOMhelpdebug',
init: function() {
if (!document.getElementById || !document.createTextNode) { return; }
},
lastSibling: function(node) {
var tempObj = node.parentNode.lastChild;
while (tempObj.nodeType != 1 && tempObj.previousSibling != null) {
tempObj = tempObj.previousSibling;
}
return (tempObj.nodeType == 1) ? tempObj : false;
},
firstSibling: function(node) {
var tempObj = node.parentNode.firstChild;
while (tempObj.nodeType != 1 && tempObj.nextSibling != null) {
tempObj = tempObj.nextSibling;
}
return (tempObj.nodeType == 1) ? tempObj : false;
},
getText: function(node) {
if (!node.hasChildNodes()) { return false; }
var reg = /^\s+$/;
var tempObj = node.firstChild;
while (tempObj.nodeType != 3 && tempObj.nextSibling != null || reg.test(tempObj.nodeValue)) {
tempObj = tempObj.nextSibling;
}
return tempObj.nodeType == 3 ? tempObj.nodeValue : false;
},
setText: function(node, txt) {
if (!node.hasChildNodes()) { return false; }
var reg = /^\s+$/;
var tempObj = node.firstChild;
while (tempObj.nodeType != 3 && tempObj.nextSibling != null || reg.test(tempObj.nodeValue)) {
tempObj = tempObj.nextSibling;
}
if (tempObj.nodeType == 3) { tempObj.nodeValue = txt } else { return false; }
},
createLink: function(to, txt) {
var tempObj = document.createElement('a');
tempObj.appendChild(document.createTextNode(txt));
tempObj.setAttribute('href', to);
return tempObj;
},
createTextElm: function(elm, txt) {
var tempObj = document.createElement(elm);
tempObj.appendChild(document.createTextNode(txt));
return tempObj;
},
closestSibling: function(node, direction) {
var tempObj;
if (direction == -1 && node.previousSibling != null) {
tempObj = node.previousSibling;
while (tempObj.nodeType != 1 && tempObj.previousSibling != null) {
tempObj = tempObj.previousSibling;
}
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tempObj = node.nextSibling;
while (tempObj.nodeType != 1 && tempObj.nextSibling != null) {
tempObj = tempObj.nextSibling;
}
}
return tempObj.nodeType == 1 ? tempObj : false;
},
initDebug: function() {
if (DOMhelp.debug) { DOMhelp.stopDebug(); }
DOMhelp.debug = document.createElement('div');
DOMhelp.debug.setAttribute('id', DOMhelp.debugWindowId);
document.body.insertBefore(DOMhelp.debug, document.body.firstChild);
},
setDebug: function(bug) {
if (!DOMhelp.debug) { DOMhelp.initDebug(); }
DOMhelp.debug.innerHTML += bug + '\n';
},
stopDebug: function() {
if (DOMhelp.debug) {
DOMhelp.debug.parentNode.removeChild(DOMhelp.debug);
DOMhelp.debug = null;
}
},
getKey: function(e) {
if (window.event) {
var key = window.event.keyCode;
} else if (e) {
var key = e.keyCode;
}
return key;
},
/* helper methods */
getTarget: function(e) {
var target = window.event ? window.event.srcElement : e ? e.target : null;
if (!target) { return false; }
while (target.nodeType != 1 && target.nodeName.toLowerCase() != 'body') {
target = target.parentNode;
}
return target;
},
stopBubble: function(e) {
if (window.event && window.event.cancelBubble) {
window.event.cancelBubble = true;
}
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}
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if (window.event && window.event.returnValue) {
window.event.returnValue = false;
}
if (e && e.preventDefault) {
e.preventDefault();
}
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cancelClick: function(e) {
if (window.event) {
window.event.cancelBubble = true;
window.event.returnValue = false;
}
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e.stopPropagation();
e.preventDefault();
}
},
addEvent: function(elm, evType, fn, useCapture) {
if (elm.addEventListener) {
elm.addEventListener(evType, fn, useCapture);
return true;
} else if (elm.attachEvent) {
var r = elm.attachEvent('on' + evType, fn);
return r;
} else {
elm['on' + evType] = fn;
}
},
cssjs: function(a, o, c1, c2) {
switch (a) {
case 'swap':
o.className = !DOMhelp.cssjs('check', o, c1) ? o.className.replace(c2, c1) : o.className.replace(c1, c2);
break;
case 'add':
if (!DOMhelp.cssjs('check', o, c1)) { o.className += o.className ? ' ' + c1 : c1; }
break;
case 'remove':
var rep = o.className.match(' ' + c1) ? ' ' + c1 : c1;
o.className = o.className.replace(rep, '');
break;
case 'check':
var found = false;
var temparray = o.className.split(' ');
for (var i = 0; i < temparray.length; i++) {
if (temparray[i] == c1) { found = true; }
}
return found;
break;
}
},
safariClickFix: function() {
return false;
}
}
DOMhelp.addEvent(window, 'load', DOMhelp.init, false);
</script>
<script type="text/javascript">
<!--
sn = {
dynamicClass: 'dyn',
showClass: 'show',
parentClass: 'parent',
openClass: 'open',
navID: 'nav',
init: function() {
var triggerLink;
if (!document.getElementById || !document.createTextNode) { return; }
var nav = document.getElementById(sn.navID);
if (!nav) { return; }
DOMhelp.cssjs('add', nav, sn.dynamicClass);
var nested = nav.getElementsByTagName('ul');
for (var i = 0; i < nested.length; i++) {
triggerLink = nested[i].parentNode.getElementsByTagName('a')[0];
DOMhelp.cssjs('add', triggerLink.parentNode, sn.parentClass);
DOMhelp.addEvent(triggerLink, 'click', sn.changeSection, false);
triggerLink.onclick = DOMhelp.safariClickFix;
if (nested[i].parentNode.getElementsByTagName('strong').length > 0) {
DOMhelp.cssjs('add', triggerLink.parentNode, sn.openClass);
DOMhelp.cssjs('add', nested[i], sn.showClass);
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},
changeSection: function(e) {
var t = DOMhelp.getTarget(e);
var firstList = t.parentNode.getElementsByTagName('ul')[0];
if (DOMhelp.cssjs('check', firstList, sn.showClass)) {
DOMhelp.cssjs('remove', firstList, sn.showClass)
DOMhelp.cssjs('swap', t.parentNode, sn.openClass, sn.parentClass);
} else {
DOMhelp.cssjs('add', firstList, sn.showClass)
DOMhelp.cssjs('swap', t.parentNode, sn.openClass, sn.parentClass);
}
DOMhelp.cancelClick(e);
}
}
DOMhelp.addEvent(window, 'load', sn.init, false);
-->
</script>
<h2>【荐】JS封装的一个无限级的下拉树形菜单_网页代码站(www.webdm.cn)</h2>
<ul id="nav">
<li><a href="#">主页</a></li>
<li><a href="#">产品</a>
<ul>
<li><a href="#">大类别一</a>
<ul>
<li><a href="#">小类别一</a>
<ul>
<li><a href="#">次类别一</a></li>
<li><a href="#">次类别二</a></li>
</ul>
</li>
<li><a href="#">小类别二</a></li>
</ul>
</li>
<li><a href="#">大类别二</a></li>
<li><a href="#">大类别三</a>
<ul>
<li><a href="#">小类别一</a></li>
<li><a href="#">小类别二</a></li>
</ul>
</li>
</ul>
</li>
<li><a href="#">服务</a>
<ul>
<li><a href="#">大类别一</a></li>
<li><a href="#">大类别二</a></li>
<li><a href="#">大类别三</a></li>
</ul>
</li>
<li><a href="#">合作</a></li>
<li><a href="#">关于我们</a>
<ul>
<li><a href="#">大类别一</a>
<ul>
<li><a href="#">小类别一</a></li>
<li><a href="#">小类别二</a></li>
</ul>
</li>
<li><a href="#">大类别二</a>
<ul>
<li><a href="#">小类别一</a></li>
<li><a href="#">小类别二</a></li>
</ul>
</li>
<li><a href="#">大类别三</a>
<ul>
<li><a href="#">小类别一</a></li>
<li><a href="#">小类别二</a></li>
</ul>
</li>
<li><a href="#">大类别四</a></li>
</ul>
</li>
<li><a href="#">联系我们</a>
<ul>
<li><a href="#">大类别一</a></li>
<li><a href="#">大类别二</a></li>
</ul>
</li>
</ul>
<br />
<p>
<a href="http://www.webdm.cn">网页代码站</a> - 最专业的网页代码下载网站 - 致力为中国站长提供有质量的网页代码！</p>
代码来自：http://www.webdm.cn/webcode/790e8b32-a44e-499f-a5a2-12c4321b356e.html