pwa-helpers/src/network.ts

/**
@license
Copyright (c) 2018 The Polymer Project Authors. All rights reserved.
This code may only be used under the BSD style license found at http://polymer.github.io/LICENSE.txt
The complete set of authors may be found at http://polymer.github.io/AUTHORS.txt
The complete set of contributors may be found at http://polymer.github.io/CONTRIBUTORS.txt
Code distributed by Google as part of the polymer project is also
subject to an additional IP rights grant found at http://polymer.github.io/PATENTS.txt
*/

/**
  Utility method that calls a callback whenever the network connectivity of the app changes.
  The callback should take a boolean parameter (with `true` meaning
  the network is offline, and `false` meaning online)

  Example:

      import { installOfflineWatcher } from 'pwa-helpers/network.js';

      installOfflineWatcher((offline) => {
        console.log('You are ' + offline ? ' offline' : 'online');
      });
*/
export const installOfflineWatcher = (offlineUpdatedCallback: (isOffline: boolean) => void) => {
  window.addEventListener('online', () => offlineUpdatedCallback(false));
  window.addEventListener('offline', () => offlineUpdatedCallback(true));

  offlineUpdatedCallback(navigator.onLine === false);
};