使用indexOf方法判断就可以了。
<script language="javascript">
var ua = navigator.userAgent.split("")
if(ua[2].indexOf("Windows NT 5.1")!=-1)
{
window.location = 'http://www.baidu.com'
}
else
{
window.location = 'http://www.google.com'
}
//document.write("'"+ua[2]+"'")
</script>
window对象有navigator属性，你把它打印出来，会发现oscpu就是操作系统的版本号。
例如：
console.log(navigator.oscpu)版本号和操作系统的对应关系如下：
'Windows 3.11' =>'Win16',
'Windows 95' =>'(Windows 95)|(Win95)|(Windows_95)',
'Windows 98' =>'(Windows 98)|(Win98)',
'Windows 2000' =>'(Windows NT 5.0)|(Windows 2000)',
'Windows XP' =>'(Windows NT 5.1)|(Windows XP)',
'Windows Server 2003' =>'(Windows NT 5.2)',
'Windows Vista' =>'(Windows NT 6.0)',
'Windows 7' =>'(Windows NT 6.1)',
'Windows 8' =>'(Windows NT 6.2)|(WOW64)',
'Windows NT 4.0' =>'(Windows NT 4.0)|(WinNT4.0)|(WinNT)|(Windows NT)',
'Windows ME' =>'Windows ME',
'Open BSD' =>'OpenBSD',
'Sun OS' =>'SunOS',
'Linux' =>'(Linux)|(X11)',
'Mac OS' =>'(Mac_PowerPC)|(Macintosh)',
'QNX' =>'QNX',
'BeOS' =>'BeOS',
'OS/2' =>'OS/2',
'Search Bot'=>'(nuhk)|(Googlebot)|(Yammybot)|(Openbot)|(Slurp)|(MSNBot)|(Ask Jeeves/Teoma)|(ia_archiver)'
