实现网页背景变暗，显示信息提示效果!

<script language="javascript">var alternateFrame=null;//生成的iframe
var alternateWin=null;window.alert=showAlert;
window.confirm=showConfirm;/**
 * 人机交互窗口，覆盖自带的
 */
function alternateWindow(){
this.win=null;//生成对话框的窗口对象
this.pBody=null;//生成的body容器对象
this.pBg=null;
this.type="open";//默认的种类是alert
this.FocusWhere="OK";//焦点在哪个按钮上
}
/**
 * 模仿的alert窗口
 */
function showAlert(info){
alternateWin=new alternateWindow();
var pBody = alternateWin.init();
alternateWin.initAlertBody(pBody,info);
alternateWin.type="alert";
}
  /**
 * 模仿的alert窗口
 */
function showConfirm(info,ok_func,notok_func,ok_str,not_okstr){
alternateWin=new alternateWindow();
var pBody = alternateWin.init();
alternateWin.initConfirmBody(pBody,info,ok_func,notok_func,ok_str,not_okstr);
alternateWin.type="confirm";
}
/**
 * 作用：初始基本信息
 */
alternateWindow.prototype.init=function() {
if(alternateFrame==null){
alternateFrame=document.createElement("<iframe allowTransparency='true' id='popframe' frameborder=0 marginheight=0 src='about:blank' marginwidth=0 hspace=0 vspace=0 scrolling=no></iframe>")
alternateFrame.style.position="absolute";
document.body.appendChild(alternateFrame);
}else{
alternateFrame.style.visibility="visible";
}
alternateFrame.style.width=screen.availWidth;
alternateFrame.style.height=screen.availHeight;
alternateFrame.style.left=document.body.scrollLeft;
alternateFrame.style.top=document.body.scrollTop;
//alternateFrame.name= "alertWin";
alternateFrame.name = alternateFrame.uniqueID;this.win=window.frames[alternateFrame.name];
this.win.document.write("<body leftmargin=0 topmargin=0 oncontextmenu='self.event.returnValue=false'><div id=popbg></div><div id=popbody></div><div></div></body>");
this.win.document.body.style.backgroundColor="transparent";
document.body.style.overflow="hidden";
this.pBody=this.win.document.body.children[1];
this.pBg=this.win.document.body.children[0];
this.hideAllSelect();
this.initBg();return this.pBody;
} /**
* 作用：初始化背景层
  */
alternateWindow.prototype.initBg=function(){
with(this.pBg.style){
position="absolute";
left="0";
top="0";
width="100%";
height="100%";
visibility="hidden";
backgroundColor="#333333";
filter="blendTrans(duration=1) alpha(opacity=30)";
}
this.pBg.filters.blendTrans.apply();
this.pBg.style.visibility="visible";
this.pBg.filters.blendTrans.play();
}
/**
 * 作用：初始化显示层
 */
alternateWindow.prototype.initAlertBody=function(obj,info){
with(obj.style){
position="absolute";
width="400";
height="150";
backgroundColor="#ffffff";
}
obj.style.left=window.document.body.clientWidth/2-200;
obj.style.top=window.document.body.clientHeight/3;
var str;
//dialogArguments.vDialog=null;
str ="<table border=0 cellpadding=0 cellspacing=1 bgcolor=#000000 width=100% height=100%><form id='form1' name='form1'><tr height=30>";
str+="<td align=left style='color:#000000;font-size:14px;font-weight:bold' bgcolor=#9999ff>[提示]</td></tr>";
str+="<tr><td align=center bgcolor=#efefff style='font-size:12px;color:#000000;vertical-align: middle;'>";
str+=info+"<input type=text id=ttt><input type=text id=rrr><input type=text id=uuu><input type='button' onclick='alert(this.name);parent.getall();' value='传递文字'></td></tr><tr height=30 bgcolor=#efefef><td align=center>" +
     "<input type='button' value='确定' id='OK'" +
     " onkeydown='parent.alternateWin.onKeyDown(event,this)'"+
     " onclick='parent.alternateWin.closeWin()' style='border:solid 1px #666666;background:#cccccc'>" +
     "</td></tr></form></table>";
obj.innerHTML=str;
this.win.document.body.all.OK.focus();
this.FocusWhere="OK";
}alternateWindow.prototype.onKeyDown=function(event,obj){
  switch(event.keyCode){
  case 9:
   event.keyCode=-1;
  if(this.type=="confirm"){
  if(this.FocusWhere=="OK"){
  this.win.document.body.all.NO.focus();
  this.FocusWhere="NO";
  }else{
  this.win.document.body.all.OK.focus();
  this.FocusWhere="OK";
  }
  }
  break;
  case 13:obj.click();;break;
  case 27:this.closeWin();break;  
  }  }/**
 * 作用：关闭一切
 */
alternateWindow.prototype.closeWin=function(){
alternateFrame.style.visibility="hidden"; 
this.showAllSelect();
document.body.style.overflow="auto"; 
}
/**
  * 作用:隐藏所有的select
  */
alternateWindow.prototype.hideAllSelect=function(){
  var obj;
  obj=document.getElementsByTagName("SELECT");
  var i;
  for(i=0;i<obj.length;i++)
obj[i].style.visibility="hidden";
  }
/**
 * 显示所有的select
 */  
  alternateWindow.prototype.showAllSelect=function(){
  var obj;
  obj=document.getElementsByTagName("SELECT");
  var i;
  for(i=0;i<obj.length;i++)
obj[i].style.visibility="visible";
}function formToRequestString(formname)
{
var query_string=''; var form_obj = window.frames[0].document.getElementById(formname).elements;
for (var i=0;i<form_obj.length ;i++)
{
var e=form_obj[i];
if (e.id!='')
{
var element_value = "";
if (e.type.toLowerCase()=='select'){
element_value=e.options[e.selectedIndex].value;
}else if (e.type.toLowerCase()=='checkbox' || e.type.toLowerCase()=='radio'){
if (e.checked==false){
continue;
}
element_value=e.value;
}else{
element_value=e.value;
}
query_string+=e.name+'='+element_value.replace(/\&/g,"%26") + '&';
} }
return query_string;
}
</script><script>   
  function getall() {
   document.getElementById("ssss").value = window.frames[0].document.getElementById("ttt").value;
  }
  </script>
<input name=ssss type=text>
<div id=naeee></div>
<body>
<button onclick="alert('');">跳出新窗口传值</button>
</body>