ngsw pwa how to check version update

// You will probably need to tell the service worker to check the server for updates, I usually use a service for this:

export class UpdateService {
  constructor(public updates: SwUpdate) {

    if (updates.isEnabled) {

      interval(6 * 60 * 60).subscribe(() => updates.checkForUpdate()

        .then(() => console.log(‘checking for updates’)));

    }

  }
  public checkForUpdates(): void {

    this.updates.available.subscribe(event => this.promptUser());

  }
  private promptUser(): void {

    console.log(‘updating to new version’);

    this.updates.activateUpdate().then(() => document.location.reload());

  }

// In your app-component.ts:
  constructor(private sw: UpdateService) {

    // check the service worker for updates

    this.sw.checkForUpdates();

  }

// For whatever reason, Angular sometimes does not register the service worker properly. So you can modify `main.ts` :

// Replace:
// platformBrowserDynamic().bootstrapModule(AppModule);

// With:
platformBrowserDynamic().bootstrapModule(AppModule).then(() => {

  if (‘serviceWorker’ in navigator && environment.production) {

    navigator.serviceWorker.register(‘ngsw-worker.js’);

  }

}).catch(err => console.log(err));