Angular service for working with geoLocations using ngCordova

geoService.js

((angular, window) => {
  /**
   * GeoLocation Utility Service
   * @param $localStorage
   * @param $cordovaGeolocation
   * @param $q
   * @returns {{getCachedGeoLocation: getCachedGeoLocation, getDistance: getDistance}}
   * @constructor
   */
  var GeoService = function($localStorage, $cordovaGeolocation, $q) {
    var $storage = $localStorage,
      cachedLocation = $storage.currentLocation,
      isUS = navigator.language.match(/us/ig);

    var isLocationExpired = () =>
      angular.isUndefined(cachedLocation)
      || cachedLocation.error
      || cachedLocation.lookupTime - +new Date() > 3E5;

    /**
     * Return the distance in miles if `navigator.language` is 'en-US' otherwise
     * returns distance in kilometers
     *
     * @param {number} distance
     * @returns {string} distance in either miles or km
     */
    var getLocaleDistance = (distance) =>
      isUS ? (distance / 1.609344).toFixed(1) + ' mi' : distance.toFixed(1) + ' km';

    /**
     * Calculates the distance between two latitude-longitude points
     *
     * Taken from {@link http://stackoverflow.com/a/7179026}
     * @param {number} lat1
     * @param {number} lon1
     * @param {number} lat2
     * @param {number} lon2
     * @returns {number}
     */
    var computeDistanceBetween = (lat1, lon1, lat2, lon2) => {
      var toRad = (val) => val * Math.PI / 180;

      var R = 6371 | 0, // Radius of the earth 6371 km
        dLat = toRad(lat2 - lat1),
        dLon = toRad(lon2 - lon1);

      var a = Math.sin(dLat / 2) * Math.sin(dLat / 2) + Math.cos(toRad(lat1)) * Math.cos(toRad(lat2)) * Math.sin(dLon / 2) * Math.sin(dLon / 2);

      var c = 2 * Math.atan(Math.sqrt(a), Math.sqrt(1 - a));
      return R * c;
    };

    this.getCachedGeoLocation = function() {
      var deferred = $q.defer();

      // Was the last lookup more than 5 min ago.
      if (!isLocationExpired()) {
        return $q.when(cachedLocation);
      } else {
        $cordovaGeolocation.getCurrentPosition().then((position) => {
          console.log(position.timestamp);
          var currentPosition = {
            'latitude': position.coords.latitude,
            'longitude': position.coords.longitude,
            'accuracy': position.coords.accuracy ,
            'lookupTime': +new Date()
          };

          $storage.currentLocation = currentPosition;
          deferred.resolve(currentPosition);
        }, (err) => {
          cachedLocation['error'] = err;
          deferred.reject(err)
        });
      }

      return deferred.promise;

    };

    /**
     * Get the distance of the building from the cached geolocation of user
     *
     * @param {number} latitude
     * @param {number} longitude
     * @returns {string} prettyDistance
     */
    this.getDistance = function(latitude, longitude) {
      return getLocaleDistance(computeDistanceBetween(cachedLocation.latitude, cachedLocation.longitude, latitude, longitude));
    }
  };

  angular.module('iOffice.geo', ['ngCordova']).service('GeoService', GeoService);
})(angular, window);