判断浏览器版本是否是ie9以下浏览器，提示升级

(function(window) {
var theUA = window.navigator.userAgent.toLowerCase();
if ((theUA.match(/msie\s\d+/) && theUA.match(/msie\s\d+/)[0]) || (theUA.match(/trident\s?\d+/) && theUA.match(/trident\s?\d+/)[0])) {
var ieVersion = theUA.match(/msie\s\d+/)[0].match(/\d+/)[0] || theUA.match(/trident\s?\d+/)[0];
if (ieVersion < 9) {
var str = "你的浏览器版本太low了,已经和时代脱轨了 :(";
var str2 = "推荐使用:<a href='https://www.baidu.com/s?ie=UTF-8&wd=%E8%B0%B7%E6%AD%8C%E6%B5%8F%E8%A7%88%E5%99%A8' target='_blank' style='color:blue;'>谷歌</a>,"
+ "<a href='https://www.baidu.com/s?ie=UTF-8&wd=%E7%81%AB%E7%8B%90%E6%B5%8F%E8%A7%88%E5%99%A8' target='_blank' style='color:blue;'>火狐</a>,"
+ "其他双核极速模式";
document.writeln("<pre style='text-align:center;color:#fff;background-color:#0cc; height:100%;border:0;position:fixed;top:0;left:0;width:100%;z-index:1234'>" +
"<h2 style='padding-top:200px;margin:0'><strong>" + str + "<br/></strong></h2><h2>" +
str2 + "</h2><h2 style='margin:0'><strong>如果你的使用的是双核浏览器,请切换到极速模式访问<br/></strong></h2></pre>");
document.execCommand("Stop");
};
}
})(window);

<!--[if lt IE 9]>
<script type="text/javascript">
var str = "你的浏览器版本太low了,已经和时代脱轨了 :(";
var str2 = "推荐使用:<a href='https://www.baidu.com/s?ie=UTF-8&wd=%E8%B0%B7%E6%AD%8C%E6%B5%8F%E8%A7%88%E5%99%A8' target='_blank' style='color:blue;'>谷歌</a>,"
+ "<a href='https://www.baidu.com/s?ie=UTF-8&wd=%E7%81%AB%E7%8B%90%E6%B5%8F%E8%A7%88%E5%99%A8' target='_blank' style='color:blue;'>火狐</a>,"
+ "其他双核极速模式";
document.writeln("<pre style='text-align:center;color:#fff;background-color:#0cc; height:100%;border:0;position:fixed;top:0;left:0;width:100%;z-index:1234'>" +
"<h2 style='padding-top:200px;margin:0'><strong>" + str + "<br/></strong></h2><h2>" +
str2 + "</h2><h2 style='margin:0'><strong>如果你的使用的是双核浏览器,请切换到极速模式访问<br/></strong></h2></pre>");
document.execCommand("Stop");
</script>
<![endif]-->