code: function(location) {
      var latitude = location.coords.latitude;
      var longitude = location.coords.longitude;
      log("Retrieved user's location: [" + latitude + ", " + longitude + "]");
  
      var username = "wesley";
      geoFire.set(username, [latitude, longitude]).then(function() {
        log("Current user " + username + "'s location has been added to GeoFire");
  
        // When the user disconnects from Firebase (e.g. closes the app, exits the browser),
        // remove their GeoFire entry
        firebaseRef.child(username).onDisconnect().remove();
  
        log("Added handler to remove user " + username + " from GeoFire when you leave this page.");
      }).catch(function(error) {
        log("Error adding user " + username + "'s location to GeoFire");
      });
    }
docs: /* Callback method from the geolocation API which receives the current user's location