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>