JavaScript 实现点击弹出提示层及背景变暗效果

<html>
<head>
<title>点击弹出提示，背景变暗</title>
<script>
function msg(info){
var p=document.createElement("DIV");
if (!info) var info='<a href="#" target="_blank" rel="external">欢迎光临</a>';
p.id="p";
p.style.position="absolute";
p.style.width=document.body.scrollWidth;
p.style.height=(document.body.offsetHeight>document.body.scrollHeight)?'100%':document.body.scrollHeight;
p.style.zIndex='998';
p.style.top='0px';
 p.style.left='0%';
p.style.backgroundColor="gray";
p.style.opacity='0.5';
p.style.filter="alpha(opacity=80)";
document.body.appendChild(p);
var p1=document.createElement("DIV");
var top=parseInt(parseInt(document.body.scrollHeight)*0.25)+document.body.scrollTop;
p1.style.position="absolute";
p1.style.width="300px";
p1.id="p1";
var left=Math.ceil(((document.body.scrollWidth)-parseInt(p1.style.width.replace('px','')))/2)+document.body.scrollLeft;
p1.style.height="200px";
p1.style.zIndex='999';
p1.style.top=top+'px';
 p1.style.left=left+'px';
p1.style.border="0px solid red";
var html="";
 html+="<center>"
 html+="<div class='p3' style='height:1px;overflow:hidden;background:red;width:294px;border-left:1px solid red;border-right:1px solid red;'></div>"
 html+="<div class='p2' style='height:1px;overflow:hidden;background:red;width:296px;border-left:1px solid red;border-right:1px solid red;'></div>"
 html+="<div class='p2' style='height:1px;overflow:hidden;background:red;width:298px;border-left:1px solid red;border-right:1px solid red;'></div>"
 html+="<div class='p1' style='height:20px;overflow:hidden;background:red;width:300px;border-left:1px solid red;border-right:1px solid red;color:#fff;font-size:9pt;font-weight:bold;text-align:left;'> ⊙ 友情提示：</div>"
html+="<div id='c' style='height:150px;width:300px;background-color:#FEEACB;overflow:hidden;border-left:1px solid red;border-right:1px solid red;padding-top:40px;font-size:9pt;'>"+info+"<br><br><br>[ <a href='javascript:this.cancle()'> 关闭</a> ]</div>"
 html+="<div class='p1' style='height:1px;overflow:hidden;background:#FEEACB;width:298px;border-left:1px solid red;border-right:1px solid red;'></div>"
 html+="<div class='p2' style='height:1px;overflow:hidden;background:#FEEACB;width:296px;border-left:1px solid red;border-right:1px solid red;'></div>"
 html+="<div class='p3' style='height:1px;overflow:hidden;background:red;width:294px;border-left:1px solid red;border-right:1px solid red'></div>"
 html+="</center>"
document.body.appendChild(p1);
p1.innerHTML=html;
var arr=document.getElementsByTagName("select");
var i=0;
while(i<arr.length){
 arr[i].style.visibility='hidden';
 i++;
}
this.cancle=function(){
document.body.removeChild(document.getElementById('p'));
document.body.removeChild(document.getElementById('p1'));
var arr=document.getElementsByTagName("select");
 var i=0;
 while(i<arr.length){
 arr[i].style.visibility='visible';
 i++;
 }
}
}
</script>
</head>
<body>
<input value='点击弹出提示' type='button' onClick='msg()' />
</body>
</html>