这个简单，给你一段简单的示例代码，你可以参考下：
html+css部分：JavaScript部分：运行效果
代码也给你放上来，你自己复制过去运行看效果吧
<!DOCTYPE html>
<html>
<head>
<meta charset=”utf-8″ />
<title>模态对话框demo</title>
<style type=”text/css”>
body,html{margin: 0px;padding: 0px;}
div.dialog{width: 500px;height: 300px;border-radius: 5px;-webkit-border-radius: 5px;-moz-border-radius: 5px;
background:white;top: 50%;margin-left: -250px;left: 50%;margin-top: -150px;position: relative;box-sizing: border-box;}
#container{width: 100%;height: 100%;position: fixed;filter: alpha(opacity=50);
background-color: rgba(0,0,0,.5);left: 0px;top: 0px;display: none;}
#close_btn{font: bold 28px/30px “microsoft yahei”;color: darkgrey;float:right;margin-right: 5px;cursor: pointer;}
#open_diaog{border-radius: 5px;-webkit-border-radius: 5px;-moz-border-radius: 5px;height: 50px;width: 150px;border: 0px;
background: deepskyblue;font: bold 6px/21px “microsoft yahei”;cursor: pointer;}
</style>
</head>
<body>
<button id=”open_diaog”>打开模态对话框</button>
<div id=”container”>
<div class=”dialog”>
<span id=”close_btn” title=”关闭”>×</span>
<h1>偶是模态对话框</h1>
</div>
</div>
<script type=”text/javascript”>
(function(){
var close_btn = document.querySelector(‘#close_btn’);
var open_diaog = document.querySelector(‘#open_diaog’)
close_btn.onmousemove = function(){
this.style.color = ‘red’;
}
close_btn.onmouseout = function(){
this.style.color = ‘darkgrey’;
}
close_btn.onclick = function(){
document.querySelector(‘#container’).style.display = ‘none’;
}
open_diaog.onclick = function(){
document.querySelector(‘#container’).style.display = ‘block’;
}
}())
</script>
</body>
</html>
有问题记得追问偶，觉得不错的点个赞，蟹蟹支持。
