JS获得浏览器版本和操作系统版本的例子

<script type="text/javascript">
 var Sys = {};
 var ua = navigator.userAgent.toLowerCase();
 var s;
  (s = ua.match(/msie ([\d.]+)/)) ? Sys.ie = s[1] :
  (s = ua.match(/firefox\/([\d.]+)/)) ? Sys.firefox = s[1] :
  (s = ua.match(/chrome\/([\d.]+)/)) ? Sys.chrome = s[1] :
  (s = ua.match(/opera.([\d.]+)/)) ? Sys.opera = s[1] :
  (s = ua.match(/version\/([\d.]+).*safari/)) ? Sys.safari = s[1] : 0;

 //以下进行测试
 if (Sys.ie) document.write('IE: ' + Sys.ie); 
 if (Sys.firefox) document.write('Firefox: ' + Sys.firefox);
 if (Sys.chrome) document.write('Chrome: ' + Sys.chrome);
 if (Sys.opera) document.write('Opera: ' + Sys.opera);
 if (Sys.safari) document.write('Safari: ' + Sys.safari);
</script>

<script type="text/javascript">
//用于获取系统版本（注意：本方法对Firefox、Chrome无效）
var ua = window.navigator.userAgent;
var osVersion = ua.split(";")[2];
var osV = osVersion.substr(osVersion.length-3,3);

switch(osV)
{
 case "5.0":
  document.write("Windows2000");
  break;
 case "5.1":
  document.write("WindowsXP");
  break;
 case "5.2":
  document.write("Windows2003");
  break;
 case "6":
  document.write("Windows Vista");
  break;
 case "6.1":
  document.write("Windows 7");
  break;
 default:
 document.write("Others");
}
</script>