一个简单的仿XP的JS下拉菜单二（转载）

xp_menu.css（样式表）
body {
 FONT-SIZE: 13px;
 MARGIN: 0px;
 SCROLLBAR-SHADOW-COLOR: silver;
 SCROLLBAR-3DLIGHT-COLOR: silver;
 LINE-HEIGHT: 20px;
 FONT-FAMILY: Verdana, 宋体;
 SCROLLBAR-DARKSHADOW-COLOR: silver;
 BACKGROUND-COLOR: #ff99cc;
 border: none;
}

DIV.MainMenuBG
{
 border-right: teal 1px solid;
 font-size: 14px;
 border-left: #ffffff 1px solid;
 cursor: default;
 color: #000000;
 border-bottom: teal 1px solid;
 font-family: Verdana, 宋体;
 position: absolute;
 background-color: #d6d3ce;
}
DIV.MainMenu
{
 border-right: #d6d3ce 1px solid;
 padding-right: 8px;
 border-top: #d6d3ce 1px solid;
 padding-left: 8px;
 padding-bottom: 1px;
 border-left: #d6d3ce 1px solid;
 cursor: default;
 padding-top: 1px;
 border-bottom: #d6d3ce 1px solid;
 position: absolute;
 background-color: #d6d3ce;
}
DIV.MainMenuOver
{
 border-right: #08246b 1px solid;
 padding-right: 8px;
 border-top: #08246b 1px solid;
 padding-left: 8px;
 padding-bottom: 1px;
 border-left: #08246b 1px solid;
 cursor: default;
 padding-top: 1px;
 border-bottom: #08246b 1px solid;
 position: absolute;
 background-color: #b5bed6;
}
DIV.MainMenuClick
{
 border-right: #636563 1px solid;
 padding-right: 8px;
 border-top: #636563 1px solid;
 padding-left: 8px;
 padding-bottom: 1px;
 border-left: #636563 1px solid;
 cursor: default;
 padding-top: 1px;
 border-bottom: #636563 1px solid;
 position: absolute;
 background-color: #dedbd6;
}
DIV.SubMenuBG
{
 border-right: #636563 1px solid;
 border-top: #636563 1px solid;
 font-size: 14px;
 visibility: hidden;
 border-left: #636563 1px solid;
 color: #000000;
 border-bottom: #636563 1px solid;
 font-family: Verdana, 宋体;
 position: absolute;
 background-color: #fffbf7;
}
DIV.SubMenu
{
 cursor: default;
 position: absolute;
}
DIV.SubMenuOver
{
 cursor: default;
 position: absolute;
}
TD.ico
{
 border-top: #dedbd6 1px solid;
 border-left: #dedbd6 1px solid;
 border-bottom: #dedbd6 1px solid;
 background-color: #dedbd6;
}
TD.icoOver
{
 border-top: #08246b 1px solid;
 border-left: #08246b 1px solid;
 border-bottom: #08246b 1px solid;
 background-color: #b5bed6;
 border-right-width: 1px;
 border-right-color: #08246b;
}
TD.text
{
 padding-right: 2px;
 border-top: #fffbf7 1px solid;
 padding-left: 5px;
 border-bottom: #fffbf7 1px solid;
 background-color: #fffbf7;
}
TD.textOver
{
 padding-right: 2px;
 border-top: #08246b 1px solid;
 padding-left: 5px;
 border-bottom: #08246b 1px solid;
 background-color: #b5bed6;
}
TD.skey
{
 padding-right: 2px;
 border-top: #fffbf7 1px solid;
 padding-left: 2px;
 border-bottom: #fffbf7 1px solid;
 background-color: #fffbf7;
}
TD.skeyOver
{
 padding-right: 2px;
 border-top: #08246b 1px solid;
 padding-left: 2px;
 border-bottom: #08246b 1px solid;
 background-color: #b5bed6;
}
TD.sub
{
 border-right: #fffbf7 1px solid;
 border-top: #fffbf7 1px solid;
 border-bottom: #fffbf7 1px solid;
 background-color: #fffbf7;
}
TD.subOver
{
 border-right: #08246b 1px solid;
 border-top: #08246b 1px solid;
 border-bottom: #08246b 1px solid;
 background-color: #b5bed6;
}
DIV.SubMenu TD
{
 font-size: 14px;
 padding-top: 2px;
}

xp_menu.js（.js包含文件）
<!--
// menu source code

//~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
//    以下为建立菜单的部分
//_______________________________________

 //菜单条的结构
 function menu_bar(name,ico,text,key,tip,skey,type,cmd) {
  this.name = name;     //名称
  this.ico = ico;      //图标
  this.text = text;     //文字
  this.key = key;      //热键
  this.tip = tip;      //提示
  this.skey = skey;     //快捷键
  this.type = type;     //命令类型，0为弹出下级菜单，1为执行一个命令(跳转到另一个文件)
  this.cmd = cmd;      //下级菜单的名称或命令字符串，根据type的值而定
 }
 
 //菜单的结构
 function menu(name) {
  this.name = name;      //名称
  this.bar = new Array();   //所包含的菜单条数组
 }
 
 //输出一已定义的主菜单，横排的
 function popMainMenu(menu,left,top,width,height) {
  
  var strHTML, posLeft, posTop, i;
  
  strHTML = "<div id='" + menu.name + "' style='left:" + left + ";top:" + top + ";width:" + width + ";height:" + height + "' class='MainMenuBG'>"
  document.write (strHTML);
  
  posLeft = 2;
  posTop = 1;
  for (i=0;i<menu.bar.length;i++) {
   strHTML = "<div id='" + menu.bar[i].name + "' nowrap style='left:" + posLeft + ";top:" + posTop + ";' class='MainMenu' " +
        "onmouseover='return menu_onmouseover(this,\"" + menu.bar[i].cmd + "\")' onmouseout='return menu_onmouseout(this)' " +
        "onclick='return menu_onclick(this,\"" + menu.bar[i].cmd + "\")' title='" + menu.bar[i].tip + "'>" + menu.bar[i].text;
   if (menu.bar[i].key!="") {
    strHTML += "(<u>" + menu.bar[i].key + "</u>)";
   }
   strHTML += "</div>";
   document.write (strHTML);
   posLeft += document.all.item(menu.bar[i].name).offsetWidth + 1;
  }
  
  strHTML = "</div>";
  document.write (strHTML);
 }
 
 //输出一个已定义的子菜单，竖排的
 function popSubMenu(menu) {
  
  var strHTML, posLeft, posTop, i;
  
  strHTML = "<div id='" + menu.name + "' style='left:20;top:30;width:244;height:300;' class='SubMenuBG'>"
  document.write (strHTML);
  
  posLeft = 1;
  posTop = 1;
  
  for (i=0;i<menu.bar.length;i++) {
   if (menu.bar[i].name!="\-") {    //如果名称不是“\-”，表示是一个普通菜单条
    strHTML = "<div id='" + menu.bar[i].name + "' style='left:" + posLeft + ";top:" + posTop + ";' class='SubMenu' " +
         "title='" + menu.bar[i].tip + "' " +
         "onmouseover='return bar_onmouseover(this," + menu.bar[i].type + ",\"" + menu.bar[i].cmd + "\")' " +
         "onmouseout='return bar_onmouseout(this," + menu.bar[i].type + ",\"" + menu.bar[i].cmd + "\")' " +
         "onclick='return bar_onclick(this," + menu.bar[i].type + ",\"" + menu.bar[i].cmd + "\")'>" +
         "  <table border=0 cellspacing=0 cellpadding=0 width=240>" +
         "    <tr>" +
         "      <td nowrap align=center width=20 id='" + menu.bar[i].name + "_ico' class='ico'>";
    if (menu.bar[i].ico!="") {
     strHTML += "<img border=0 width=16 height=16 src='" + menu.bar[i].ico + "'>";
    }else {
     strHTML += "&nbsp;";
    }
    strHTML += "</td>" +
         "      <td nowrap id='" + menu.bar[i].name + "_text' class='text'>" + menu.bar[i].text;
    if (menu.bar[i].key!="") { strHTML = strHTML + "(<u>" + menu.bar[i].key + "</u>)"; }
    strHTML += "</td>" +
         "<td nowrap align=right id='" + menu.bar[i].name + "_skey' class='skey'>";
    if (menu.bar[i].skey!="") {
     strHTML += menu.bar[i].skey;
    }else {
     strHTML += "&nbsp;";
    }
    strHTML += "     </td>" +
         "      <td nowrap align=center width=20 id='" + menu.bar[i].name + "_sub' class='sub'>";
    if (menu.bar[i].type==0) {
     strHTML += "→";
    }else {
     strHTML += "&nbsp;&nbsp;";
    }
    strHTML += "</td>" +
         "    </tr>" +
         "  </table>" +
         "</div>";
    document.write (strHTML);
    posTop += document.all.item(menu.bar[i].name).offsetHeight;
   }else {       //如果名称是“\-”，表示是一条分隔线
    strHTML = "<div style='left:" + posLeft + ";top:" + posTop + ";' class='SubMenu'>" +
         "  <table border=0 cellpadding=0 cellspacing=0 width=240>" +
         "    <tr>" +
         "      <td nowrap style='background-color: #dedbd6;' width=21></td>" +
         "      <td nowrap style='padding-left:5px;padding-top:1px;padding-bottom:1px;'>" +
         "        <table border=0 cellpadding=0 cellspacing=0 width=100%>" +
         "          <tr><td height=1 bgcolor='#636563'></td></tr>" +
         "        </table>" +
         "      </td>" +
         "    </tr>" +
         "  </table>" +
         "</div>";
    document.write (strHTML);
    posTop += 3;
   }
  }
  
  strHTML = "</div>"
  document.write (strHTML);
  document.all.item(menu.name).style.height = posTop+3;    //重设子菜单背景框
 }

//~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
//    以下为操纵菜单的部分
//_________________________________________________

 function showMenu(menu,submenu) {  //显示一级子菜单
  document.all.item(submenu).style.left = menu.parentElement.offsetLeft + menu.offsetLeft + 1;   //设置子菜单位置
  document.all.item(submenu).style.top = menu.parentElement.offsetTop + menu.offsetTop + menu.offsetHeight -1;   //设置子菜单的位置
  document.all.item(submenu).style.visibility = "visible";   //显示子菜单
  mnuPrev[mnuPrev.length] = new menuinfo(submenu,1);   //将新打开的子菜单的ID加入当前显示菜单ID数组
 }
 
 function showSubMenu(menu,submenu) {  //显示二级及以下子菜单
  document.all.item(submenu).style.left = menu.parentElement.offsetLeft + menu.offsetLeft + menu.offsetWidth + 2;   //设置子菜单位置
  document.all.item(submenu).style.top = menu.parentElement.offsetTop + menu.offsetTop + 1;   //设置子菜单的位置
  if (document.all.item(submenu).offsetLeft + document.all.item(submenu).offsetWidth > doc_width) {
   document.all.item(submenu).style.left = menu.parentElement.offsetLeft - document.all.item(submenu).offsetWidth + 1;
  }
  if (document.all.item(submenu).offsetTop + document.all.item(submenu).offsetHeight > doc_height) {
   document.all.item(submenu).style.top = document.all.item(submenu).offsetTop + menu.offsetHeight - document.all.item(submenu).offsetHeight + 2;
  }
  document.all.item(submenu).style.visibility = "visible";   //显示子菜单
  mnuPrev[mnuPrev.length] = new menuinfo(submenu,1);   //将新打开的子菜单的ID加入当前显示菜单ID数组
 }
 
 function showstatus() {   //测试阶段用的函数，显示当前菜单ID数组内的内容
  lblMsg.innerText = "";
  for(var i=0;i<mnuPrev.length;i++) {
   lblMsg.innerText += mnuPrev[i].id + " > ";
  }
 }
 
 function menuinfo(id,type) {
  this.id = id;    //0表示菜单项，1表示菜单框
  this.type = type;
 }

 function menu_onmouseover(obj,cmd) {
  if(!mClick) {
   obj.className = "MainMenuOver";
   mnuPrev[mnuPrev.length] = new menuinfo(obj.id,0);    //将当前的菜单ID压入当前菜单ID数组
   //showstatus();   //调试阶段使用
  }else {
   if (mnuPrev[0].id == obj.id) { return false; }   //如果是在本身上移动，不作为
   document.all.item(mnuPrev[0].id).className = "MainMenu";
   for (var i=1;i<mnuPrev.length;i++) {
    if (mnuPrev[i].type==0) {   //如果是菜单项，设置成默认样式
     document.all.item(mnuPrev[i].id + "_ico").className = "ico";
     document.all.item(mnuPrev[i].id + "_text").className = "text";
     document.all.item(mnuPrev[i].id + "_skey").className = "skey";
     document.all.item(mnuPrev[i].id + "_sub").className = "sub";
    }else {   //如果是菜单框，隐藏它
     document.all.item(mnuPrev[i].id).style.visibility = "hidden";
    }
   }
   mnuPrev.length = 0;
   obj.className = "MainMenuClick";
   mnuPrev[mnuPrev.length] = new menuinfo(obj.id,0);
   showMenu(obj,cmd);
   //showstatus();   //调试阶段使用
  }
 }

 function menu_onmouseout(obj) {
  if(!mClick) {
   obj.className = "MainMenu";
   mnuPrev.length --;   //清除最后一个压入当前菜单ID数组的菜单ID
   //showstatus();   //调试阶段使用
  }
 }
 
 function menu_onclick(obj,cmd) {
  if(!mClick) {    //如果菜单当前状态是非点击状态，证明当前是从非点击状态到点击状态
   obj.className = "MainMenuClick";    //设置当前菜单为鼠标单击之后的状态
   showMenu(obj,cmd);    //显示子菜单
   //showstatus();   //调试阶段使用
   mClick = true;   //设置菜单当前是点击状态
  }else {
   obj.className = "MainMenuOver";    //设置当前菜单为鼠标移动上面的状态，非点击状态
   document.all.item(mnuPrev[mnuPrev.length-1].id).style.visibility = "hidden";
   mnuPrev.length --;
   //showstatus();   //调试阶段使用
   mClick = false;    //主菜单当前是非点击状态
  }
  bMenuClick = true;   //在一个菜单上单击后设置其状态为true,用来屏蔽document_click事件
 }

 function bar_onmouseover(obj,type,cmd) {
  for (var i=1;i<mnuPrev.length;i++) {
   if(mnuPrev[i].id==obj.parentElement.id) {
    for (var j=i+1;j<mnuPrev.length;j++) {    //处理由前一个菜单项打开的子菜单，可能有多层
     if (mnuPrev[j].type==0) {   //如果是菜单项，设置成默认样式
      document.all.item(mnuPrev[j].id + "_ico").className = "ico";
      document.all.item(mnuPrev[j].id + "_text").className = "text";
      document.all.item(mnuPrev[j].id + "_skey").className = "skey";
      document.all.item(mnuPrev[j].id + "_sub").className = "sub";
     }else {   //如果是菜单框，隐藏它
      document.all.item(mnuPrev[j].id).style.visibility = "hidden";
     }
    }
    mnuPrev.length = i + 1;
    break;
   }
  }
  mnuPrev[mnuPrev.length] = new menuinfo(obj.id,0);
  //showstatus();   //调试阶段使用
  document.all.item(obj.id + "_ico").className = "icoOver";
  document.all.item(obj.id + "_text").className = "textOver";
  document.all.item(obj.id + "_skey").className = "skeyOver";
  document.all.item(obj.id + "_sub").className = "subOver";
  if (type==0) { showSubMenu(obj,cmd); }   //如果有下一级菜单就展开
  //showstatus();   //调试阶段使用
 }
  
 function bar_onmouseout(obj,type,cmd) {
  if (type!=0) {
   document.all.item(obj.id + "_ico").className = "ico";
   document.all.item(obj.id + "_text").className = "text";
   document.all.item(obj.id + "_skey").className = "skey";
   document.all.item(obj.id + "_sub").className = "sub";
   if (mnuPrev.length>0) {
    mnuPrev.length --;
   }
   
   //showstatus();   //调试阶段使用
  }
 }

 function bar_onclick(obj,type,cmd) {
  if (type==1) {
   //window.navigate(cmd);   //跳转到相应的文件
   lblOutput.innerText = cmd; //演示期间，将文件名显示出来
  }else {
   bMenuClick = true;   //在一个菜单上单击后设置其状态为true,用来屏蔽document_click事件
  }
 }

//~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
//    以下为与主文件有关的控制部分，具体使用时需要关注的也仅仅这部分而已
//_____________________________________________________________

 var doc_width;    //当前窗口的宽度，随窗口大小改变而改变
 var doc_height;    //当前窗口的高度，随窗口大小改变而改变
 
 var mClick = false;   //一级菜单是否被点击，初始一级菜单是未被点击状态
 var bMenuClick = false;    //单击是否是在一个菜单上，初始单击不是在一个菜单上
 var mnuPrev = new Array();   //当前显示的菜单ID数组，初始为空

 function document_onselectstart() {
  return false;    //屏蔽内容选择功能
 }

 function document_onclick() {
  if(!bMenuClick) {
   if (mnuPrev.length>0) {
    for (var i=1;i<mnuPrev.length;i++) {
     if (mnuPrev[i].type==0) {   //如果是菜单项，设置成默认样式
      document.all.item(mnuPrev[i].id + "_ico").className = "ico";
      document.all.item(mnuPrev[i].id + "_text").className = "text";
      document.all.item(mnuPrev[i].id + "_skey").className = "skey";
      document.all.item(mnuPrev[i].id + "_sub").className = "sub";
     }else {   //如果是菜单框，隐藏它
      document.all.item(mnuPrev[i].id).style.visibility = "hidden";
     }
    }
    document.all.item(mnuPrev[0].id).className = "MainMenu";    //将主菜单的状态恢复普通状态
   }
   mnuPrev.length = 0;    //清空当前显示菜单
   mClick = false;    //清除菜单点击状态
  }else {
   bMenuClick = false;
  }
 }

 function window_onresize() {
  //当窗口尺寸变化时改变相应变量的值
  doc_height = window.document.body.offsetHeight;
  doc_width = window.document.body.offsetWidth;
 }

 function window_onload() {
  //初始化窗口尺寸
  doc_height = window.document.body.offsetHeight;
  doc_width = window.document.body.offsetWidth;
 }

//-->