仿DVBBS下拉菜单效果

//Pop-it menu- By Dynamic Drive - Modified by Wbird
//For full source code and more DHTML scripts, visit http://www.gyct.cn
//This credit MUST stay intact for use
var menuOffX=0 //菜单距连接文字最左端距离
var menuOffY=18 //菜单距连接文字顶端距离
var vBobjects = new Array();
var fo_shadows=new Array()
////No need to edit beyond here
var ie4=document.all&&navigator.userAgent.indexOf("Opera")==-1
var ns6=document.getElementById&&!document.all
var ns4=document.layers

function MM_findObj(n, d) {
var p,i,x;  if(!d) d=document; if((p=n.indexOf("?"))>0&&parent.frames.length) {
d=parent.frames[n.substring(p+1)].document; n=n.substring(0,p);}

if(!(x=d[n])&&d.all) x=d.all[n]; for (i=0;!x&&i<d.forms.length;i++) x=d.forms[n];
  
for(i=0;!x&&d.layers&&i<d.layers.length;i++) x=MM_findObj(n,d.layers.document);
  
if(!x && d.getElementById) x=d.getElementById(n); return x;

}

function fetch_object(idname, forcefetch)
{
if (typeof(vBobjects[idname]) == "undefined")
{
  vBobjects[idname] = MM_findObj(idname);
}
return vBobjects[idname];
}
//showmenu vmenu:内容，允许为空,vmenuobj DIV数据ID，MOD 0=关闭浏览器自适应，用于版面导航菜单
function showmenu(e,vmenu,vmenuobj,mod){
if (!document.all&&!document.getElementById&&!document.layers)
  return
var which=vmenu;
if (vmenuobj)
{
  var MenuObj = fetch_object(vmenuobj);
  if (MenuObj)
  {
   which = MenuObj.innerHTML;
  }
}
if (!which)
{
  return
}
clearhidemenu();
ie_clearshadow();
menuobj=ie4? document.all.popmenu : ns6? document.getElementById("popmenu") : ns4? document.popmenu : ""
menuobj.thestyle=(ie4||ns6)? menuobj.style : menuobj
if (ie4||ns6)
  menuobj.innerHTML=which
else{
  menuobj.document.write('<layer name=gui bgcolor="#E6E6E6" width="165" onmouseover="clearhidemenu()" onmouseout="hidemenu()">'+which+'</layer>')
  menuobj.document.close()
}
menuobj.contentwidth=(ie4||ns6)? menuobj.offsetWidth : menuobj.document.gui.document.width
menuobj.contentheight=(ie4||ns6)? menuobj.offsetHeight : menuobj.document.gui.document.height
eventX=ie4? event.clientX : ns6? e.clientX : e.x
eventY=ie4? event.clientY : ns6? e.clientY : e.y
var rightedge=ie4? document.body.clientWidth-eventX : window.innerWidth-eventX
var bottomedge=ie4? document.body.clientHeight-eventY : window.innerHeight-eventY
var getlength
  if (rightedge<menuobj.contentwidth){
   getlength=ie4? document.body.scrollLeft+eventX-menuobj.contentwidth+menuOffX : ns6? window.pageXOffset+eventX-menuobj.contentwidth : eventX-menuobj.contentwidth
  }else{
   getlength=ie4? ie_x(event.srcElement)+menuOffX : ns6? window.pageXOffset+eventX : eventX
  }
  menuobj.thestyle.left=getlength+'px'
  if (bottomedge<menuobj.contentheight&&mod!=0){
   getlength=ie4? document.body.scrollTop+eventY-menuobj.contentheight-event.offsetY+menuOffY-23 : ns6? window.pageYOffset+eventY-menuobj.contentheight-10 : eventY-menuobj.contentheight
  } else{
   getlength=ie4? ie_y(event.srcElement)+menuOffY : ns6? window.pageYOffset+eventY+10 : eventY
  }
menuobj.thestyle.top=getlength+'px'
menuobj.thestyle.visibility="visible"
ie_dropshadow(menuobj,"#999999",3)
return false
}

function ie_y(e){  
var t=e.offsetTop;  
while(e=e.offsetParent){  
  t+=e.offsetTop;  
}  
return t;  
}  
function ie_x(e){  
var l=e.offsetLeft;  
while(e=e.offsetParent){  
  l+=e.offsetLeft;  
}  
return l;  
}  
function ie_dropshadow(el, color, size)
{
var i;
for (i=size; i>0; i--)
{
  var rect = document.createElement('div');
  var rs = rect.style
  rs.position = 'absolute';
  rs.left = (el.style.posLeft + i) + 'px';
  rs.top = (el.style.posTop + i) + 'px';
  rs.width = el.offsetWidth + 'px';
  rs.height = el.offsetHeight + 'px';
  rs.zIndex = el.style.zIndex - i;
  rs.backgroundColor = color;
  var opacity = 1 - i / (i + 1);
  rs.filter = 'alpha(opacity=' + (100 * opacity) + ')';
  //el.insertAdjacentElement('afterEnd', rect);
  fo_shadows[fo_shadows.length] = rect;
}
}
function ie_clearshadow()
{
for(var i=0;i<fo_shadows.length;i++)
{
  if (fo_shadows)
   fo_shadows.style.display="none"
}
fo_shadows=new Array();
}


function contains_ns6(a, b) {
while (b.parentNode)
  if ((b = b.parentNode) == a)
   return true;
return false;
}

function hidemenu(){
if (window.menuobj)
  menuobj.thestyle.visibility=(ie4||ns6)? "hidden" : "hide"
ie_clearshadow()
}

function dynamichide(e){
if (ie4&&!menuobj.contains(e.toElement))
  hidemenu()
else if (ns6&&e.currentTarget!= e.relatedTarget&& !contains_ns6(e.currentTarget, e.relatedTarget))
  hidemenu()
}

function clearhidemenu(){
if (window.delayhide)
  clearTimeout(delayhide)
}

if (ie4||ns6)
document.onclick=hidemenu