javascript 判断系统设备

<script>

function detectOS() { 
var sUserAgent = navigator.userAgent; 

var isWin = (navigator.platform == "Win32") || (navigator.platform == "Windows"); 
var isMac = (navigator.platform == "Mac68K") || (navigator.platform == "MacPPC") || (navigator.platform == "Macintosh") || (navigator.platform == "MacIntel"); 
if (isMac) return "Mac"; 
var isUnix = (navigator.platform == "X11") && !isWin && !isMac; 
if (isUnix) return "Unix"; 
var isLinux = (String(navigator.platform).indexOf("Linux") > -1); 

var bIsAndroid = sUserAgent.toLowerCase().match(/android/i) == "android";
if (isLinux) {
if(bIsAndroid) return "Android";
else return "Linux"; 
}
if (isWin) { 
var isWin2K = sUserAgent.indexOf("Windows NT 5.0") > -1 || sUserAgent.indexOf("Windows 2000") > -1; 
if (isWin2K) return "Win2000"; 
var isWinXP = sUserAgent.indexOf("Windows NT 5.1") > -1 || 
sUserAgent.indexOf("Windows XP") > -1; 
if (isWinXP) return "WinXP"; 
var isWin2003 = sUserAgent.indexOf("Windows NT 5.2") > -1 || sUserAgent.indexOf("Windows 2003") > -1; 
if (isWin2003) return "Win2003"; 
var isWinVista= sUserAgent.indexOf("Windows NT 6.0") > -1 || sUserAgent.indexOf("Windows Vista") > -1; 
if (isWinVista) return "Vista"; 
var isWin7 = sUserAgent.indexOf("Windows NT 6.1") > -1 || sUserAgent.indexOf("Windows 7") > -1; 
if (isWin7) return "Windows 7"; 

 var isWin8 = sUserAgent.indexOf("Windows NT 6.2") > -1 || sUserAgent.indexOf("Windows 8") > -1;
if (isWin8)return "Windows8";
} 
return "other"; 
} 

document.writeln("您的操作系统是：" + detectOS()); 
alert(detectOS());

</script>