本文实例讲述了jquery实现简单的二级导航下拉菜单效果。分享给大家供大家参考。具体如下：

jQuery代码实现的二级导航菜单效果，非常简洁，喜欢简洁风格的朋友您可以下载哦。菜单最多支持两级，CSS的配合也是挺重要的，不多说了，要代码的就直接复制吧。

运行效果截图如下：

在线演示地址如下：

http://demo.jb51.net/js/2015/jquery-2jxl-menu-codes/

具体代码如下：

<title>jquery二级导航菜单</title><style>.ddsmoothmenu { MARGIN: 0px auto; FONT: 12px Verdana; WIDTH: 730px}.ddsmoothmenu UL { PADDING-RIGHT: 0px; PADDING-LEFT: 0px;BACKGROUND: #2b9801; Z-INDEX: 100; FLOAT: left; PADDING-BOTTOM: 0px; MARGIN: 0px; PADDING-TOP: 0px; LIST-STYLE-TYPE: none}.ddsmoothmenu UL LI { DISPLAY: block; FLOAT: left; WIDTH: 81px; LINE-HEIGHT: 31px; POSITION: relative; TEXT-ALIGN: center} HTML .ddsmoothmenu UL LI { FLOAT: left; WIDTH: 81px; LINE-HEIGHT: 31px; POSITION: relative; TEXT-ALIGN: center}.ddsmoothmenu UL LI A { DISPLAY: block; FONT-WEIGHT: bold; WIDTH: 81px; TEXT-DECORATION: none}.ddsmoothmenu UL LI A:link { COLOR: #fff}.ddsmoothmenu UL LI A:visited { COLOR: #fff}.ddsmoothmenu UL LI A:hover { COLOR: #ffff00}.ddsmoothmenu UL LI UL { LEFT: 0px; VISIBILITY: hidden; POSITION: absolute}.ddsmoothmenu UL LI UL LI { BACKGROUND: #2b9801; FLOAT: left; WIDTH: 81px; LINE-HEIGHT: 25px; BORDER-BOTTOM: #96d47d 1px solid}.ddsmoothmenu UL LI UL LI A { DISPLAY: block; WIDTH: 81px; TEXT-DECORATION: none}.ddsmoothmenu UL LI UL LI A:hover { BACKGROUND: #51b228}.ddsmoothmenu UL LI UL LI UL { TOP: 0px}.downarrowclass { DISPLAY: none; POSITION: absolute}.rightarrowclass { DISPLAY: none; POSITION: absolute}.ddshadow { BACKGROUND: silver; LEFT: 0px; WIDTH: 0px; POSITION: absolute; TOP: 0px; HEIGHT: 0px}.toplevelshadow { opacity: 0.8}</style><SCRIPT src="jquery1.3.2.js" type=text/javascript></SCRIPT><SCRIPT type=text/javascript>var ddsmoothmenu={//Specify full URL to down and right arrow images (23 is padding-right added to top level LIs with drop downs):arrowimages: {down:['downarrowclass', '', 0], right:['rightarrowclass', '']},transition: {overtime:300, outtime:300}, //duration of slide in/ out animation, in millisecondsshadow: {enabled:false, offsetx:5, offsety:5},detectwebkit: navigator.userAgent.toLowerCase().indexOf("applewebkit")!=-1, //detect WebKit browsers (Safari, Chrome etc)getajaxmenu:function($, setting){ //function to fetch external page containing the panel DIVs var $menucontainer=$('#'+setting.contentsource[0]) //reference empty div on page that will hold menu $menucontainer.html("Loading Menu...") $.ajax({ url: setting.contentsource[1], //path to external menu file async: true, error:function(ajaxrequest){ $menucontainer.html('Error fetching content. Server Response: '+ajaxrequest.responseText) }, success:function(content){ $menucontainer.html(content) ddsmoothmenu.buildmenu($, setting) } })},buildshadow:function($, $subul){},buildmenu:function($, setting){ var smoothmenu=ddsmoothmenu var $mainmenu=$("#"+setting.mainmenuid+">ul") //reference main menu UL var $headers=$mainmenu.find("ul").parent() $headers.each(function(i){ var $curobj=$(this).css({zIndex: 100-i}) //reference current LI header var $subul=$(this).find('ul:eq(0)').css({display:'block'}) this._dimensions={w:this.offsetWidth, h:this.offsetHeight, subulw:$subul.outerWidth(), subulh:$subul.outerHeight()} this.istopheader=$curobj.parents("ul").length==1? true : false //is top level header? $subul.css({top:this.istopheader? this._dimensions.h+"px" : 0}) $curobj.children("a:eq(0)").css(this.istopheader? {paddingRight: smoothmenu.arrowimages.down[2]} : {}).append( //add arrow images '<img src="'+ (this.istopheader? smoothmenu.arrowimages.down[1] : smoothmenu.arrowimages.right[1]) +'" class="' + (this.istopheader? smoothmenu.arrowimages.down[0] : smoothmenu.arrowimages.right[0]) + '" style="border:0;" />' ) if (smoothmenu.shadow.enabled){ this._shadowoffset={x:(this.istopheader?$subul.offset().left+smoothmenu.shadow.offsetx : this._dimensions.w), y:(this.istopheader? $subul.offset().top+smoothmenu.shadow.offsety : $curobj.position().top)} //store this shadow's offsets if (this.istopheader) $parentshadow=$(document.body) else{ var $parentLi=$curobj.parents("li:eq(0)") $parentshadow=$parentLi.get(0).$shadow } this.$shadow=$('<div class="ddshadow'+(this.istopheader? ' toplevelshadow' : '')+'"></div>').prependTo($parentshadow).css({left:this._shadowoffset.x+'px', top:this._shadowoffset.y+'px'}) //insert shadow DIV and set it to parent node for the next shadow div } $curobj.hover( function(e){ var $targetul=$(this).children("ul:eq(0)") this._offsets={left:$(this).offset().left, top:$(this).offset().top} var menuleft=this.istopheader? 0 : this._dimensions.w menuleft=(this._offsets.left+menuleft+this._dimensions.subulw>$(window).width())? (this.istopheader? -this._dimensions.subulw+this._dimensions.w : -this._dimensions.w) : menuleft //calculate this sub menu's offsets from its parent if ($targetul.queue().length<=1){ //if 1 or less queued animations $targetul.css({left:menuleft+"px", width:this._dimensions.subulw+'px'}).animate({height:'show',opacity:'show'}, ddsmoothmenu.transition.overtime) if (smoothmenu.shadow.enabled){ var shadowleft=this.istopheader? $targetul.offset().left+ddsmoothmenu.shadow.offsetx : menuleft var shadowtop=this.istopheader?$targetul.offset().top+smoothmenu.shadow.offsety : this._shadowoffset.y if (!this.istopheader && ddsmoothmenu.detectwebkit){ //in WebKit browsers, restore shadow's opacity to full this.$shadow.css({opacity:1}) } this.$shadow.css({overflow:'', width:this._dimensions.subulw+'px', left:shadowleft+'px', top:shadowtop+'px'}).animate({height:this._dimensions.subulh+'px'}, ddsmoothmenu.transition.overtime) } } }, function(e){ var $targetul=$(this).children("ul:eq(0)") $targetul.animate({height:'hide', opacity:'hide'}, ddsmoothmenu.transition.outtime) if (smoothmenu.shadow.enabled){ if (ddsmoothmenu.detectwebkit){ //in WebKit browsers, set first child shadow's opacity to 0, as "overflow:hidden" doesn't work in them this.$shadow.children('div:eq(0)').css({opacity:0}) } this.$shadow.css({overflow:'hidden'}).animate({height:0}, ddsmoothmenu.transition.outtime) } } ) //end hover }) //end $headers.each() $mainmenu.find("ul").css({display:'none', visibility:'visible'})},init:function(setting){ if (typeof setting.customtheme=="object" && setting.customtheme.length==2){ var mainmenuid='#'+setting.mainmenuid document.write('<style type="text/css">\n' +mainmenuid+', '+mainmenuid+' ul li a {background:'+setting.customtheme[0]+';}\n' +mainmenuid+' ul li a:hover {background:'+setting.customtheme[1]+';}\n' +'</style>') } jQuery(document).ready(function($){ //override default menu colors (default/hover) with custom set? if (typeof setting.contentsource=="object"){ //if external ajax menu ddsmoothmenu.getajaxmenu($, setting) } else{ //else if markup menu ddsmoothmenu.buildmenu($, setting) } })}} //end ddsmoothmenu variable//Initialize Menu instance(s):ddsmoothmenu.init({ mainmenuid: "smoothmenu1", //menu DIV id customtheme: [], //override default menu CSS background values? Uncomment: ["normal_background", "hover_background"] contentsource: "markup" //"markup" or ["container_id", "path_to_menu_file"]})</SCRIPT><DIV class=ddsmoothmenu id=smoothmenu1><UL> <LI><A href="#">首页</A> </LI> <LI><A href="#">一年级</A> <UL> <LI><A href="#">一年级1班</A> </LI> <LI><A href="#">一年级2班</A> </LI> <LI><A href="#">一年级3班</A> </LI> <LI><A href="#">一年级4班</A> </LI> <LI><A href="#">一年级5班</A> </LI></UL></LI> <LI><A href="#">二年级</A> <UL> <LI><A href="#">二年级1班</A> </LI> <LI><A href="#">二年级2班</A> </LI> <LI><A href="#">二年级3班</A> </LI> <LI><A href="#">二年级4班</A> </LI> <LI><A href="#">二年级5班</A> </LI></UL></LI> <LI><A href="#">三年级</A> <UL> <LI><A href="#">三年级1班</A> </LI> <LI><A href="#">三年级2班</A> </LI> <LI><A href="#">三年级3班</A> </LI> <LI><A href="#">三年级4班</A> </LI> <LI><A href="#">三年级5班</A> </LI></UL></LI><LI><A href="#">四年级</A> <UL> <LI><A href="#">四年级1班</A> </LI> <LI><A href="#">四年级2班</A> </LI> <LI><A href="#">四年级3班</A> </LI> <LI><A href="#">四年级4班</A> </LI> <LI><A href="#">四年级5班</A> </LI></UL></LI> <LI><A href="#">五年级</A> <UL> <LI><A href="#">五年级1班</A> </LI> <LI><A href="#">五年级2班</A> </LI> <LI><A href="#">五年级3班</A> </LI> <LI><A href="#">五年级4班</A> </LI> <LI><A href="#">五年级5班</A> </LI></UL></LI> <LI><A href="#">六年级</A> <UL> <LI><A href="#">六年级1班</A> </LI> <LI><A href="#">六年级2班</A> </LI> <LI><A href="#">六年级3班</A> </LI> <LI><A href="#">六年级4班</A> </LI> <LI><A href="#">六年级5班</A> </LI></UL></LI> <LI><A href="#">七年级</A> <UL> <LI><A href="#">七年级1班</A> </LI> <LI><A href="#">七年级2班</A> </LI> <LI><A href="#">七年级3班</A> </LI> <LI><A href="#">七年级4班</A> </LI> <LI><A href="#">七年级5班</A> </LI></UL></LI></UL></DIV>

希望本文所述对大家的jquery程序设计有所帮助。