js模拟windows系统自定义多级右键菜单

js模拟系统右键效果，在网页中右击鼠标，弹窗类似windows桌面上右击类似效果

截图如下：

在线预览地址：http://www.lanrenzhijia.com/demo/1221/nav/

下载地址：http://www.lanrenzhijia.com/nav/2061.html

部分JS代码：

var getOffset = {
 top: function (obj) {
  return obj.offsetTop + (obj.offsetParent ? arguments.callee(obj.offsetParent) : 0)
 },
 left: function (obj) {
  return obj.offsetLeft + (obj.offsetParent ? arguments.callee(obj.offsetParent) : 0)
 } 
};
window.onload = function ()
{
 var oMenu = document.getElementById("rightMenu");
 var aUl = oMenu.getElementsByTagName("ul");
 var aLi = oMenu.getElementsByTagName("li");
 var showTimer = hideTimer = null;
 var i = 0;
 var maxWidth = maxHeight = 0;
 var aDoc = [document.documentElement.offsetWidth, document.documentElement.offsetHeight];
 
 oMenu.style.display = "none";
 
 for (i = 0; i < aLi.length; i++)
 {
  //为含有子菜单的li加上箭头
  aLi[i].getElementsByTagName("ul")[0] && (aLi[i].className = "sub");
  
  //鼠标移入
  aLi[i].onmouseover = function ()
  {
   var oThis = this;
   var oUl = oThis.getElementsByTagName("ul");
   
   //鼠标移入样式
   oThis.className += " active";   
   
   //显示子菜单
   if (oUl[0])
   {
    clearTimeout(hideTimer);    
    showTimer = setTimeout(function ()
    {
     for (i = 0; i < oThis.parentNode.children.length; i++)
     {
      oThis.parentNode.children[i].getElementsByTagName("ul")[0] &&
      (oThis.parentNode.children[i].getElementsByTagName("ul")[0].style.display = "none");
     }
     oUl[0].style.display = "block";
     oUl[0].style.top = oThis.offsetTop + "px";
     oUl[0].style.left = oThis.offsetWidth + "px";
     setWidth(oUl[0]);
     
     //最大显示范围     
     maxWidth = aDoc[0] - oUl[0].offsetWidth;
     maxHeight = aDoc[1] - oUl[0].offsetHeight;
     
     //防止溢出
     maxWidth < getOffset.left(oUl[0]) && (oUl[0].style.left = -oUl[0].clientWidth + "px");
     maxHeight < getOffset.top(oUl[0]) && (oUl[0].style.top = -oUl[0].clientHeight + oThis.offsetTop + oThis.clientHeight + "px")
    },300);
   }   
  };
   
  //鼠标移出 
  aLi[i].onmouseout = function ()
  {
   var oThis = this;
   var oUl = oThis.getElementsByTagName("ul");
   //鼠标移出样式
   oThis.className = oThis.className.replace(/\s?active/,"");
   
   clearTimeout(showTimer);
   hideTimer = setTimeout(function ()
   {
    for (i = 0; i < oThis.parentNode.children.length; i++)
    {
     oThis.parentNode.children[i].getElementsByTagName("ul")[0] &&
     (oThis.parentNode.children[i].getElementsByTagName("ul")[0].style.display = "none");
    }
   },300);
  };
 } 
 
 
 //自定义右键菜单
 document.oncontextmenu = function (event)
 {
  var event = event || window.event;
  oMenu.style.display = "block";
  oMenu.style.top = event.clientY + "px";
  oMenu.style.left = event.clientX + "px";
  setWidth(aUl[0]);
  
  //最大显示范围
  maxWidth = aDoc[0] - oMenu.offsetWidth;
  maxHeight = aDoc[1] - oMenu.offsetHeight;
  
  //防止菜单溢出
  oMenu.offsetTop > maxHeight && (oMenu.style.top = maxHeight + "px");
  oMenu.offsetLeft > maxWidth && (oMenu.style.left = maxWidth + "px");
  return false;
 };
 
 //点击隐藏菜单
 document.onclick = function ()
 {
  oMenu.style.display = "none" 
 };
 
 //取li中最大的宽度, 并赋给同级所有li 
 function setWidth(obj)
 {
  maxWidth = 0;
  for (i = 0; i < obj.children.length; i++)
  {
   var oLi = obj.children[i];   
   var iWidth = oLi.clientWidth - parseInt(oLi.currentStyle ? oLi.currentStyle["paddingLeft"] : getComputedStyle(oLi,null)["paddingLeft"]) * 2
   if (iWidth > maxWidth) maxWidth = iWidth;
  }
  for (i = 0; i < obj.children.length; i++) obj.children[i].style.width = maxWidth + "px";
 }
};