Distance between two gps locations

dist2GPS.js

const dist2GPS = (lat1, lng1, lat2, lng2) => {
  lat1 = parseFloat(lat1);
  lng1 = parseFloat(lng1);
  lat2 = parseFloat(lat2);
  lng2 = parseFloat(lng2);

  const R = 6371e3;
  const φ1 = lat1.toRad();
  const φ2 = lat2.toRad();
  const Δφ = (lat2 - lat1).toRad();
  const Δλ = (lng2 - lng1).toRad();

  const a =
    Math.sin(Δφ / 2) * Math.sin(Δφ / 2) +
    Math.cos(φ1) * Math.cos(φ2) * Math.sin(Δλ / 2) * Math.sin(Δλ / 2);
  const c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1 - a));

  // return R * c; //meters
  return R * c * 0.000621371192; // miles;
};

if (typeof Number.prototype.toRad === 'undefined') {
  // eslint-disable-next-line no-extend-native
  Number.prototype.toRad = function() {
    return (this * Math.PI) / 180;
  };
}

export default dist2GPS;