js弹出的对话窗口永远保持居中显示

复制代码 代码如下:

  <!DOCTYPE html>

  <html lang="en" xmlns="http://www.w3.org/1999/xhtml">

  <head>

  <meta charset="utf-8" />

  <title></title>

  <style type="text/css">

  .Div_Scroll {

  position:fixed;

  margin:-10px;

  visibility:hidden;

  background-color:#808080;

  opacity:0.6;

  z-index:99;

  }

  .Div_Scroll_Content {

  position:relative;

  margin-top:20%;

  width:inherit;

  height:inherit;

  }

  .Div_AlertWindow {

  margin:auto;

  width:200px;

  height:100px;

  background-color:lightblue;

  border:5px solid #f00;

  }

  </style>

  <script type="text/javascript">

  window.onload = function () {

  var alertWindow = $("alertParent");

  alertWindow.style.width = window.screen.availWidth + "px";

  alertWindow.style.height = window.screen.height + "px";

  $("Sure").onclick = function () {

  alertWindow.style.visibility = "hidden";

  }

  }

  function ShowAlert() {

  var alertWindow = $("alertParent");

  alertWindow.style.visibility = "visible";

  }

  $ = function (id) {

  return document.getElementById(id);

  }

  </script>

  </head>

  <body>

  <div id="alertParent" class="Div_Scroll">

  <div class="Div_Scroll_Content">

  <div id="AlertWindow" class="Div_AlertWindow">

  <input type="button" id="Sure" value="close alert Dialog..." />

  </div>

  </div>

  </div>

  <div style="height:1300px; padding-top:200px;" >

  <input id="alertButton" type="button" onclick="ShowAlert();" value="Show alert Dialog..."/>

  </div>

  </body>

  </html>

  添加遮罩层