原生js实现半透明遮罩层效果具体代码

代码如下:

<!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>弹出提示</title>
<style>
* {
margin: 0;
padding: 0;
font-size: 12px;
}
html, body {
height: 100%;
width: 100%;
}
#content {
background: #FFFFFF;
padding: 30px;
height: 100%;
}
#content a {
font-size: 30px;
color: #369;
font-weight: 700;
}
#alert { z-index:2;
border: 1px solid #369;
width: 300px;
height: 150px;
background: #e2ecf5;
z-index: 1000;
position: absolute;
display: none;
}
#alert h4 {
height: 20px;
background: #369;
color: #fff;
padding: 5px 0 0 5px;
}
#alert h4 span {
float: left;
}
#alert h4 span#close {
margin-left: 210px;
font-weight: 500;
cursor: pointer;
}
#alert p {
padding: 12px 0 0 30px;
}
#alert p input {
width: 120px;
margin-left: 20px;
}
#alert p input.myinp {
border: 1px solid #ccc;
height: 16px;
}
#alert p input.sub {
width: 60px;
margin-left: 30px;
}
#mask{ position:absolute; top:0; left:0; height:100%; width:100%; background:#000; opacity:0.3; display:none; z-index:1;}
</style>
</head>
<body>
<div id="content"> <a href="#">注册</a> </div>
<div id="alert">
<h4><span>现在注册</span><span id="close">关闭</span></h4>
<p>
<label> 用户名</label>
<input type="text" class="myinp" onmouseover="this.style.border='1px solid #f60'" onfoucs="this.style.border='1px solid #f60'" onblur="this.style.border='1px solid #ccc'" />
</p>
<p>
<label> 密　码</label>
<input type="password" class="myinp" onmouseover="this.style.border='1px solid #f60'" onfoucs="this.style.border='1px solid #f60'" onblur="this.style.border='1px solid #ccc'" />
</p>
<p>
<input type="submit" value="注册" class="sub" />
<input type="reset" value="重置" class="sub" />
</p>
</div>
<div id="mask"></div><!-- 遮罩层div-->
<script type="text/javascript">
var myAlert = document.getElementById("alert");
var myMask=document.getElementById('mask');
var reg = document.getElementById("content").getElementsByTagName("a")[0];
var mClose = document.getElementById("close");
reg.onclick = function()
{
myMask.style.display="block";
myAlert.style.display = "block";
myAlert.style.position = "absolute";
myAlert.style.top = "50%";
myAlert.style.left = "50%";
myAlert.style.marginTop = "-75px";
myAlert.style.marginLeft = "-150px";
document.body.style.overflow = "hidden";
}
mClose.onclick = function()
{
myAlert.style.display = "none";
myMask.style.display = "none";
}
</script>
</body>
</html>