javascript如何获取本机的操作系统类型

function GetOSInfo()
{ 
  var _pf=navigator.platform; 
  var appVer=navigator.userAgent; 
  if(_pf=="Win32" || _pf == "Windows") 
  { 
    if(appVer.indexOf("WOW64")>-1)
    { 
      _bit = "64位"; 
    }
    else
    { 
      _bit = "32位"; 
    } 
    if(appVer.indexOf("Windows NT 6.0") > -1 || appVer.indexOf("Windows Vista") > -1) 
    { 
      if(_bit=='64位' || appVer.indexOf("Windows Vista") > -1)
      { 
        return 'Windows_vista '+_bit; 
      }
      else
      { 
        return "Unknow1"; 
      } 
    }
    else if(appVer.indexOf("Windows NT 6.1") > -1 || appVer.indexOf("Windows 7") > -1) 
    { 
      if(_bit=='32位' || appVer.indexOf("Windows 7") > -1)
      { 
        return 'Windows_7 '+_bit; 
      }
      else
      { 
        return "Unknow"; 
      } 
    }
    else
    { 
      try
      { 
        var _winName = Array('2000','XP','2003'); 
        var _ntNum = appVer.match(/Windows NT 5.\d/i).toString(); 
        return 'Windows_' + _winName[_ntNum.replace(/Windows NT 5.(\d)/i,"$1")]+" "+_bit; 
      }
      catch(e)
      {
        return 'Windows';
      } 
    } 
  }
  else if(_pf == "Mac68K" || _pf == "MacPPC" || _pf == "Macintosh") 
  { 
    return "Mac"; 
  }
  else if(_pf == "X11") 
  { 
    return "Unix"; 
  }
  else if(String(_pf).indexOf("Linux") > -1) 
  { 
    return "Linux"; 
  }
  else
  { 
    return "Unknow"; 
  } 
}