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);

    if (isLinux) 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 "WinVista";

        var isWin7 = sUserAgent.indexOf("Windows NT 6.1") > -1 || sUserAgent.indexOf("Windows 7") > -1;

        if (isWin7) return "Win7";

var isWin8 = sUserAgent.indexOf("Windows NT 6.2") > -1 || sUserAgent.indexOf("Windows 8") > -1;
             if (isWin8) return "Win8";
             var isWin81 = sUserAgent.indexOf("Windows NT 6.3") > -1 || sUserAgent.indexOf("Windows 8.1") > -1;
             if (isWin81) return "Win8.1";

    }

    return "other";

}

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