js 页面中弹出小窗口,页面背景直接变半透明

<style>
html,body {
	font-size: 12px;
	margin: 0px;
	height: 100%;
}

.mesWindow {
	border: #666 1px solid;
	background: #fff;
}

.mesWindowTop {
	border-bottom: #eee 1px solid;
	margin-left: 4px;
	padding: 3px;
	font-weight: bold;
	text-align: left;
	font-size: 12px;
}

.mesWindowContent {
	margin: 4px;
	font-size: 12px;
}

.mesWindow .close {
	height: 15px;
	width: 28px;
	border: none;
	cursor: pointer;
	text-decoration: underline;
	background: #fff
}
</style>
<script>
var isIe=(document.all)?true:false;
//设置select的可见状态
function setSelectState(state)
{
var objl=document.getElementsByTagName('select');
for(var i=0;i<objl.length;i++)
{
objl[i].style.visibility=state;
}
}


function mousePosition(ev)
{
if(ev.pageX || ev.pageY)
{
return {x:ev.pageX, y:ev.pageY};
}
return {
x:ev.clientX + document.body.scrollLeft - document.body.clientLeft,y:ev.clientY + document.body.scrollTop - document.body.clientTop
};
}


//弹出方法
function showMessageBox(wTitle,content,pos,wWidth)
{
closeWindow();
var bWidth=parseInt(document.documentElement.scrollWidth);
var bHeight=parseInt(document.documentElement.scrollHeight);
if(isIe){
setSelectState('hidden');}
var back=document.createElement("div");
back.id="back";
var styleStr="top:0px;left:0px;position:absolute;background:#666;width:"+bWidth+"px;height:"+bHeight+"px;";
styleStr+=(isIe)?"filter:alpha(opacity=40);":"opacity:0.40;";
back.style.cssText=styleStr;
document.body.appendChild(back);
var mesW=document.createElement("div");
mesW.id="mesWindow";
mesW.className="mesWindow";
mesW.innerHTML="<div class='mesWindowTop'><table width='100%' height='100%'><tr><td>"+wTitle+"</td><td style='width:1px;'><input type='button' οnclick='closeWindow();' title='关闭窗口' class='close' value='关闭' /></td></tr></table></div><div class='mesWindowContent' id='mesWindowContent'>"+content+"</div><div class='mesWindowBottom'></div>";
styleStr="left:"+(((pos.x-wWidth)>0)?(pos.x-wWidth):pos.x)+"px;top:"+(pos.y)+"px;position:absolute;width:"+wWidth+"px;";
mesW.style.cssText=styleStr;
document.body.appendChild(mesW);
}

function showBackground(obj,endInt)
{
obj.filters.alpha.opacity+=1;
if(obj.filters.alpha.opacity<endInt)
{
setTimeout(function(){showBackground(obj,endInt)},8);
}
}

//关闭窗口
function closeWindow()
{
if(document.getElementById('back')!=null)
{
document.getElementById('back').parentNode.removeChild(document.getElementById('back'));
}
if(document.getElementById('mesWindow')!=null)
{
document.getElementById('mesWindow').parentNode.removeChild(document.getElementById('mesWindow'));
}
if(isIe){
setSelectState('');}
}

//测试弹出
function testMessageBox(ev)
{
var objPos = mousePosition(ev);
messContent="<div style='padding:20px 0 20px 0;text-align:center'>消息正文</div>";
showMessageBox('窗口标题',messContent,objPos,350);
}



</script>
<div style="padding: 20px">
	<div style="text-align: left";>
		<a href="#none" οnclick="testMessageBox(event);">弹出窗口</a>
	</div>
</div>