Source: geo-position.js

  1. import { logger } from "./shims";
  3. const initialGeoTimeoutSeconds = 1;
  5. const defaultCoords = {
  6.   latitude: 1,
  7.   longitude: 1
  8. };
  10. // for an initial rapid, low-accuracy position
  11. const fastGeolocationPositionOptions = { 
  12.   enableHighAccuracy: false,
  13.   timeout: initialGeoTimeoutSeconds
  14. };
  16. // subsequent position monitoring should be high-accuracy
  17. const accurateGeolocationPositionOptions = { 
  18.   enableHighAccuracy: true
  19. };
  21. /** Responsible for tracking the user's position, when geo listening is enabled and the browser is capable
  22.  * @property {Boolean} geoListenEnabled - whether or not the geo positioning system is enabled and available
  23.  * @see https://developer.mozilla.org/en-US/docs/Web/API/Geolocation/Using_geolocation **/
  24. export class GeoPosition {
  25.   /** Create a new GeoPosition.
  26.    * @param {Object} navigator - provides access to geolocation system
  27.    * @param {Object} options - parameters for initializing this GeoPosition
  28.    * @param {Boolean} [options.geoListenEnabled = false] - whether or not to attempt to use geolocation **/
  29.   constructor(navigator,options = {}) {
  30.     this._navigator = navigator;
  31.     this._initialGeolocationPromise = Promise.resolve(defaultCoords);
  33.     if (this._navigator.geolocation && options.geoListenEnabled) {
  34.       this.geoListenEnabled = true;
  35.     } else {
  36.       this.geoListenEnabled = false;
  37.     }
  38.   }
  40.   /** @return {String} Human-readable representation of this GeoPosition **/
  41.   toString() { 
  42.     return `GeoPosition (enabled: ${this.geoListenEnabled})`;
  43.   }
  45.   /** Attempts to get an initial rough geographic location for the listener, then sets up a callback
  46.    * to update the position.
  47.    * @param {Function} geoUpdateCallback - object that should receive geolocation coordinate updates
  48.    * @see geoListenEnabled **/
  49.   connect(geoUpdateCallback = () => {}) {
  50.     if (!this.geoListenEnabled) {
  51.       logger.info("Geolocation disabled");
  52.       this._initialGeolocationPromise = Promise.resolve({});
  53.       return;
  54.     }
  56.     logger.info("Initializing geolocation system");
  58.     this._initialGeolocationPromise = new Promise((resolve,reject) => {
  59.       this._navigator.geolocation.getCurrentPosition((initialPosition) => {
  60.         let coords = initialPosition.coords;
  61.         logger.info("Received initial geolocation",coords);
  62.         geoUpdateCallback(coords);
  64.         let geoWatchId = this._navigator.geolocation.watchPosition((updatedPosition) => {
  65.           let newCoords = updatedPosition.coords;
  66.           geoUpdateCallback(newCoords);
  67.         },(error) => {
  68.           logger.warn(`Unable to watch position: ${error.message} (code #${error.code})`);
  69.         },accurateGeolocationPositionOptions);
  71.         logger.info(`Monitoring geoposition updates (watch ID ${geoWatchId})`);
  72.         resolve(coords);
  73.       },function initialGeoError(error) {
  74.         logger.warn(`Unable to get initial geolocation: ${error.message} (code #${error.code})`);
  75.         resolve(defaultCoords);
  76.       },fastGeolocationPositionOptions);
  77.     });
  78.   }
  80.   /** Allows you to wait on the progress of the .connect() behavior, attempting to get an initial
  81.    * estimate of the user's position. Note that this promise will never fail - if we cannot get an
  82.    * accurate estimate, we fall back to default coordinates (currently latitude 1, longitude 1)
  83.    * @return {Promise} Represents the attempt to get an initial estimate of the user's position **/
  84.   waitForInitialGeolocation() {
  85.     return this._initialGeolocationPromise;
  86.   }
  87. }