jquery实现简单的二级导航下拉菜单效果

<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>