Dumb browser detection...

stupid.js

/**
 * Determines (poorly) the current browser.
 * @returns {string} the current browser or 'unknown'.
 */
function getBrowser() {
  var ua = navigator.userAgent;
  var browsers = [
    'Vivaldi',
    'OPR', // Opera
    'Firefox',
    'Chrome',
    'Safari'
  ];
  
  for ( let i = 0, length = browsers.length; i < length; i++ ) {
    if ( ua.includes( browsers[i] ) ) {
      return browsers[i];
    }
  }
  
  return 'unknown';
}