JavaScript snippet to detect the user operating system

detectOS.js

function detectOs() {
  let userAgt = navigator.userAgent;
  let os = '';
  let version = '';
  let regOsVersion = '';
  let osMap = [
    { s : 'Windows', r:/(Windows 10.0|Windows NT 10.0|Windows 8.1|Windows NT 6.3|Windows 8|Windows NT 6.2|Windows 7|Windows NT 6.1)/},
    { s : 'Linux', r:/(Linux|X11(?!.*CrOS))/},
    { s : 'Mac OS X', r:/Mac OS X/},
    { s : 'Mac OS', r:/(Mac OS|MacPPC|MacIntel|Mac_PowerPC|Macintosh)/}
  ];
  for (let id in osMap) {
    let cs = osMap[id];
    if (cs.r.test(userAgt)) {
      os = cs.s;
      regOsVersion = cs.r;
      break;
    }
  }
  switch(os) {
    case 'Windows':
      if (regOsVersion.exec(userAgt)[0].indexOf('NT 10.0') || regOsVersion.exec(userAgt)[0].indexOf('10.0') ) {
        version = '10';
      } else if (regOsVersion.exec(userAgt)[0].indexOf('8.1') || regOsVersion.exec(userAgt)[0].indexOf('NT 6.3')) {
        version = '8.1';
      } else if (regOsVersion.exec(userAgt)[0].indexOf('8') || regOsVersion.exec(userAgt)[0].indexOf('NT 6.2')) {
        version = '8';
      } else if (regOsVersion.exec(userAgt)[0].indexOf('7') || regOsVersion.exec(userAgt)[0].indexOf('NT 6.1')) {
        version = '7';
      }
      break;
    case 'Mac OS X':
      version = userAgt.split('Mac OS X ')[1].split(')')[0];
      version = version.split(';')[0].replaceAll('_', '.');
      break;
    case 'Mac OS':
      version = '';
      break;
    case 'Linux':
      version = '';
      break;
  }
  return os + ' ' + version;
};
detectOs();