JS遮盖

用JavaScript做一个遮盖(Iframe和div)，但是当页面本身有Scrollbar时，弹出的遮盖层却始终无法遮盖住Scrollbar。本人推测原因可能是Iframe和div的添加方式导致它们不可能覆盖掉原有页面的Scrollbar，具体的代码如下：
document.body.appendChild(iframe);
document.body.appendChild(div);
这样一来Iframe和div都属于body中的元素，它们就不可能遮盖body之外的元素(页面本身的Scrollbar属于整个HTML这个根节点)
但是某天在浏览gmail时却发现google完美地实现了此功能(gmail-->设置-->选择图片)。
任何想法或解决方案都是受欢迎的。

解决方案 »

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是不是GOOGLE的页面本身就处于一个frame中呢.
就像这样
<frame>
GAMIL
</frame>然后在frame里面弹出层?
function showDiv()
{
var arrySize = getPageSize();
var overlayDiv =document.createElement("div");
overlayDiv.id = "overlay";
document.body.appendChild(oDiv);
overlayDiv.style.height = arrySize[1];
overlayDiv.style.width = arrySize[0];
overlayDiv.style.display = "block";
}
function getPageSize(){

var xScroll, yScroll;

if (window.innerHeight && window.scrollMaxY) {
xScroll = document.body.scrollWidth;
//alert(xScroll);
yScroll = window.innerHeight + window.scrollMaxY;
} else if (document.body.scrollHeight > document.body.offsetHeight){ // all but Explorer Mac
xScroll = document.body.scrollWidth;
yScroll = document.body.scrollHeight;
} else { // Explorer Mac...would also work in Explorer 6 Strict, Mozilla and Safari
xScroll = document.body.offsetWidth;
//alert(xScroll);
yScroll = document.body.offsetHeight;
}

var windowWidth, windowHeight;
if (self.innerHeight) { // all except Explorer
//alert('all except Explorer');
windowWidth = self.innerWidth;
windowHeight = self.innerHeight;
//alert(windowWidth +'all except Explorer'+windowHeight);
} else if (document.documentElement && document.documentElement.clientHeight) { // Explorer 6 Strict Mode
windowWidth = document.documentElement.clientWidth;
windowHeight = document.documentElement.clientHeight;
} else if (document.body) { // other Explorers
//alert('other Explorers');
windowWidth = document.body.clientWidth;
windowHeight = document.body.clientHeight;
}

// for small pages with total height less then height of the viewport
if(yScroll < windowHeight){
pageHeight = windowHeight;
} else {
pageHeight = yScroll;
} // for small pages with total width less then width of the viewport
if(xScroll < windowWidth){
pageWidth = windowWidth;
} else {
pageWidth = xScroll;
} //alert('pageWidth ' + pageWidth + " pageHeight " +pageHeight + " windowWidth "+ windowWidth + " windowHeight "+windowHeight);
arrayPageSize = new Array(pageWidth,pageHeight,windowWidth,windowHeight)
return arrayPageSize;
}
又看了一下，整个显示应该是就是一个充满页面的iframe,遮盖层盖住的也只是iframe罢了 (在页面中遮盖iFrame)
iFrame的滚动条充当页面的滚动条，要确保的是iFrame永远不会超出页面高度，页面的滚动条此时无用且永远不该出现
<!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></title>
<STYLE>
#login{
 position: relative;
 display: none;
 top: 20px;
 left: 30px;
 background-color: #ffffff;
 text-align: center;
 border: solid 1px;
 padding: 10px;
 z-index: 1;
}

</STYLE>
<script type="text/javascript">
var W = screen.width;//取得屏幕分辨率宽度
var H = screen.height;//取得屏幕分辨率高度function M(id){
return document.getElementById(id);//用M()方法代替document.getElementById(id)
}
function MC(t){
return document.createElement(t);//用MC()方法代替document.createElement(t)
};
//判断浏览器是否为IE
function isIE(){
 return (document.all && window.ActiveXObject && !window.opera) ? true : false;
}
//取得页面的高宽
function getBodySize(){
var bodySize = [];
with(document.documentElement) {
bodySize[0] = (scrollWidth>clientWidth)?scrollWidth:clientWidth;//如果滚动条的宽度大于页面的宽度，取得滚动条的宽度，否则取页面宽度
bodySize[1] = (scrollHeight>clientHeight)?scrollHeight:clientHeight;//如果滚动条的高度大于页面的高度，取得滚动条的高度，否则取高度
}
return bodySize;
}
//创建遮盖层
function popCoverDiv(){
if (M("cover_div")) {
//如果存在遮盖层，则让其显示
M("cover_div").style.display = 'block';
} else {
//否则创建遮盖层
var coverDiv = MC('div');
document.body.appendChild(coverDiv);
coverDiv.id = 'cover_div';
with(coverDiv.style) {
 position = 'absolute';
 background = '#CCCCCC';
 left = '0px';
 top = '0px';
 var bodySize = getBodySize();
 width = bodySize[0] + 'px'
 height = bodySize[1] + 'px';
 zIndex = 0;
 if (isIE()) {
 filter = "Alpha(Opacity=60)";//IE逆境
 } else {
 opacity = 0.6;
 }
}
}
}
//让登陆层显示为块
function showLogin()
{
var login=M("login");
 login.style.display = "block";
}//设置DIV层的样式
function change(){
 var login = M("login");
 login.style.position = "absolute";
 login.style.border = "1px solid #CCCCCC";
 login.style.background ="#F6F6F6";
 var i=0;
 var bodySize = getBodySize();
 login.style.left = (bodySize[0]-i*i*4)/2+"px";
 login.style.top = (bodySize[1]/2-100-i*i)+"px";
 login.style.width = i*i*4 + "px";
 login.style.height = i*i*1.5 + "px";

 popChange(i);
}
//让DIV层大小循环增大
function popChange(i){
 var login = M("login");
 var bodySize = getBodySize();
 login.style.left = (bodySize[0]-i*i*4)/2+"px";
 login.style.top = (bodySize[1]/2-100-i*i)+"px";
 login.style.width = i*i*4 + "px";
 login.style.height = i*i*1.5+ "px";
 if(i<=10){
 i++;
 setTimeout("popChange("+i+")",10);//设置超时10毫秒
 }
}
//打开DIV层
function open()
{
change();
showLogin();
popCoverDiv()
void(0);//不进行任何操作,如：<a href="#">aaa</a>
}
//关闭DIV层
function close(){
 M('login').style.display = 'none';
 M("cover_div").style.display = 'none';
void(0);
}</script>
</head><body><a href="javascript:open();">登陆</a><div id="login">
 用户登陆
<div id="panel">
<lable>用户名: </lable><input type="text" size="20" />
<lable>密码: </lable><input type="password" size="20">
<input type="checkbox" /><lable>登陆</lable>
</div>
<input type="button" value="提交" />
<a href="javascript:close();">关闭</a>
</div>
</body>
</html>
div一定要带上样式：position: absolute;  和 z-index: 3;    数字3可以变的很大，是显示遮盖优先级的控制。absolute;是浮动的意思。
测试：IE6, FF3.5
<!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=utf-8" />
<title>danica</title>
<style type="text/css">
*{padding:0;margin:0;}
html,body{width:100%;height:100%;background:#0f0;overflow:hidden;}
.content{
width:100%;height:100%;
background:#00f;
overflow:auto;
}
.shadow{
width:100%;height:100%;
overflow:hidden;
background:#f00;
opacity:0.3;
filter:alpha(opacity=30);
position:absolute;left:0;top:0;
}
</style>
</head>
<body>
<div class="shadow"></div>
<div class="content">
sdfdsfsdf1111111sdfdsfsdfsdfdsfsdfsdfdsfsdfsdfdsfsdfsdfdsfsdfsdfdsfsdfsdfdsfsdfsdfdsfsdfsdfdsfsdfsdfdsfsdfsdfdsfsdfsdfdsfsdfsdfdsfsdfsdfdsfsdfsdfdsfsdfsdfdsfsdfsdfdsfsdfsdfdsfsdfsdfdsfsdfsdfdsfsdfsdfdsfsdfsdfdsfsdfsdfdsfsdfsdfdsfsdfsdfdsfsdfsdfdsfsdfsdfdsfsdfsdfdsfsdfsdfdsfsdfsdfdsfsdfsdfdsfsdfsdfdsfsdfsdfdsfsdfsdfdsfsdfsdfdsfsdfsdfdsfsdfsdfdsfsdfsdfdsfsdfsdfdsfsdfsdfdsfsdfsdfdsfsdfsdfdsfsdfsdfdsfsdfsdfdsfsdfsdfdsfsdfsdfdsfsdfsdfdsfsdfsdfdsfsdfsdfdsfsdfsdfdsfsdfsdfdsfsdfsdfdsfsdfsdfdsfsdfsdfdsfsdfsdfdsfsdfsdfdsfsdfsdfdsfsdfsdfdsfsdfsdfdsfsdfsdfdsfsdfsdfdsfsdfsdfdsfsdfsdfdsfsdfsdfdsfsdfsdfdsfsdfsdfdsfsdf222222
</div>
</body>
</html>