知识要点
1.遮罩层的宽度和高度是js获取页面的宽高（页面内容）
//获取遮罩层(内容)的高度和宽度 var sHeight=document.documentElement.scrollHeight; var sWidth=document.documentElement.scrollWidth;
2.登录框设置静止定位fixed
3.登录框居中显示公式：(可视区域宽高-登录框宽高)/2
//获取login的宽度和高度并设置偏移值 var dHeight=oLogin.offsetHeight; var dWidth=oLogin.offsetWidth; oLogin.style.left=(sWidth-dWidth)/2+"px"; oLogin.style.top=(wHeight-dHeight)/2+"px";
完整代码
<!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>demo</title>
<style>
body,h1,h2,h3,h4,h5,h6,hr,p,blockquote,dl,dt,dd,ul,ol,li,pre,form,fieldset,legend,button,input,textarea,th,td{margin:0;padding:0;}
body,button,input,select,textarea{font:12px/1.5 tahoma,arial,\5b8b\4f53;}
h1,h2,h3,h4,h5,h6{font-size:100%;}
address,cite,dfn,em,var{font-style:normal;}
code,kbd,pre,samp{font-family:courier new,courier,monospace;}
small{font-size:12px;}
ul,ol{list-style:none;}
a{text-decoration:none;}
a:hover{text-decoration:underline;}
sup{vertical-align:text-top;}
sub{vertical-align:text-bottom;}
legend{color:#000;}
fieldset,img{border:0;}
button,input,select,textarea{font-size:100%;}
table{border-collapse:collapse;border-spacing:0;}
.clear{clear: both;float: none;height: 0;overflow: hidden;}
p{font-size: 100px;}
#mask{
background: #000;
opacity: 0.75;
filter: alpha(opacity=75);
height: 1000px;
width: 100%;
position: absolute;
left: 0;
top: 0;
z-index: 1000;
}
#login{
position: fixed;
left: 30%;
top: 30%;
z-index:1001;
}
.loginCon{
width: 670px;
height: 380px;
background: #fff;
border:5px solid #F01400;
}
#close{
width: 30px;
height: 30px;
background: blue;
cursor: pointer;
position: absolute;
right: 10px;
top: 10px;
}
#btnLogin{
width: 80px;
height: 40px;
background: #F01400;
margin:0 auto;
display: block;
cursor: pointer;
border-style: none;
color: #fff;
font-size: 16px;
}
</style>
</head>
<body>
<button id="btnLogin">登录</button>
<!--
<div id="mask"></div>
<div id="login">
<div class="loginCon">
<div id="close"></div>
</div>
</div>
-->
<p>1</p>
<p>1</p>
<p>1</p>
<p>1</p>
<p>1</p>
<p>1</p>
<p>1</p>
<p>1</p>
<p>1</p>
<p>1</p>
<script type="text/javascript">
function openNew(){
//获取页面body！内容！的高度和宽度
var sHeight=document.documentElement.scrollHeight;
var sWidth=document.documentElement.scrollWidth;
//获取可视区域高度，宽度与页面内容的宽度一样
var wHeight=document.documentElement.clientHeight;
//创建遮罩层div并插入body
var oMask=document.createElement("div");
oMask.id="mask";
oMask.style.height=sHeight+"px";
//宽度直接用100%在样式里
document.body.appendChild(oMask);
//创建登录层div并插入body
var oLogin=document.createElement("div");
oLogin.id="login";
oLogin.innerHTML="<div class='loginCon'><div id='close'></div></div>"
document.body.appendChild(oLogin);
//获取login的宽度和高度并设置偏移值
var dHeight=oLogin.offsetHeight;
var dWidth=oLogin.offsetWidth;
oLogin.style.left=(sWidth-dWidth)/2+"px";
oLogin.style.top=(wHeight-dHeight)/2+"px";
//获取关闭按钮
var oClose=document.getElementById("close");
oMask.onclick=oClose.onclick=function(){
document.body.removeChild(oMask);
document.body.removeChild(oLogin);
}
}
window.onload=function(){
var oBtn=document.getElementById("btnLogin");
oBtn.onclick=function(){
openNew();
}
}
</script>
</body>
</html>
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