因为看了很多人在找这弹出窗口效果，又不想太复杂所以把我写过的在这里分享给大家！(添加了渐显背景效果)
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=gb2312" />
<title>JS最简单的弹出窗口效果http://www.86y.org</title>
<style type="text/css">
html,body{font-size:12px;margin:0px;height:100%;}
#BOX_overlay {background:#666;left:0;position:absolute;top:0;z-index:100;}/**遮罩层的样式**/
#layer_box {background:#fff;border:3px solid #000;position:absolute;display:none;z-index:999;width:600px;} /**弹出窗口的样式**/
.box_title {background:#FFF;border-bottom:1px solid #DDD;margin:10px 10px 0;padding:0 0 5px 20px;} /**关闭栏目**/
.box_title span {font-size:14px;font-weight:bold;}
.box_title a {color:#000;position:absolute;right:10px;top:10px;}
.box_content{padding:10px;margin:10px;}
</style>
<script>
function BOX_show(e,a)//显示
{
if (document.getElementById(e) == null) {
return;
}
if (!a) {
var selects = document.getElementsByTagName("select");
for (i = 0; i < selects.length; i++) {
selects[i].style.visibility = "hidden";
}
}
BOX_layout(e);
window.onresize = function() { BOX_layout(e); } //改变窗体重新调整位置
window.onscroll = function() { BOX_layout(e); } //滚动窗体重新调整位置
document.onkeyup = function(event) {
var evt = window.event || event;
var code = evt.keyCode ? evt.keyCode : evt.which;
//alert(code);
if (code == 27) {
BOX_remove(e);
}
}
}
function BOX_remove(e)//移除
{
window.onscroll = null;
window.onresize = null;
document.getElementById("BOX_overlay").style.display = "none";
document.getElementById(e).style.display = "none";
var selects = document.getElementsByTagName("select");
for (i = 0; i < selects.length; i++) {
selects[i].style.visibility = "visible";
}
}
function BOX_layout(e)//调整位置
{
var a = document.getElementById(e);
if (document.getElementById("BOX_overlay") == null)//判断是否新建遮掩层
{
var overlay = document.createElement("div");
overlay.setAttribute("id", "BOX_overlay");
//overlay.onclick=function(){BOX_remove(e);};
//a.parentNode.appendChild(overlay);
document.body.appendChild(overlay);
}
document.getElementById("BOX_overlay").style.cssText="filter:alpha(opacity=0);-moz-opacity:0;opacity:0;"
showBackground(document.getElementById("BOX_overlay"),50)
document.getElementById("BOX_overlay").ondblclick = function() { BOX_remove(e); };
//取客户端左上坐标，宽，高
var scrollLeft = (document.documentElement.scrollLeft ? document.documentElement.scrollLeft : document.body.scrollLeft);
var scrollTop = (document.documentElement.scrollTop ? document.documentElement.scrollTop : document.body.scrollTop);
var clientWidth;
if (window.innerWidth) {
clientWidth = window.innerWidth;
//clientWidth = ((Sys.Browser.agent === Sys.Browser.Safari) ? window.innerWidth : Math.min(window.innerWidth, document.documentElement.clientWidth));
}
else {
clientWidth = document.documentElement.clientWidth;
}
var clientHeight;
if (window.innerHeight) {
clientHeight = window.innerHeight;
//clientHeight = ((Sys.Browser.agent === Sys.Browser.Safari) ? window.innerHeight : Math.min(window.innerHeight, document.documentElement.clientHeight));
}
else {
clientHeight = document.documentElement.clientHeight;
}
var bo = document.getElementById("BOX_overlay");
bo.style.left = scrollLeft + "px";
bo.style.top = scrollTop + "px";
bo.style.width ="100%";
bo.style.height = clientHeight + "px";
bo.style.display ="";
//Popup窗口定位
a.style.display = "block"
a.style.left = scrollLeft + ((clientWidth - a.offsetWidth) / 2) + "px";
a.style.top = scrollTop + ((clientHeight - a.offsetHeight) / 2) + "px";
}
function showBackground(obj,endInt)
{
var isIe=(document.all)?true:false;
if(isIe)
{
obj.filters.alpha.opacity+=2;
if(obj.filters.alpha.opacity<endInt)
{
setTimeout(function(){showBackground(obj,endInt)},5);
//alert(obj.filters.alpha.opacity);
}
}else
{
var al=parseFloat(obj.style.opacity);al+=0.01;
obj.style.opacity=al;
if(al<(endInt/100))
{setTimeout(function(){showBackground(obj,endInt)},5);}
}
}
</script>
</head>
<body>
<a href="javascript:BOX_show('layer_box');">点击弹出窗口</a>
<div id="layer_box">
<div class="box_title"><span>弹出窗口标题</span><a onclick="BOX_remove('layer_box')" href="javascript:void(0)">关闭</a></div>
<div class="box_content">弹出窗口内容</div>
</div>
</body>
</html>