Ofir Fridman's example for blog post

pollingOnResolved.ts

export function pollingOnResolved(httpRequest$: Observable<any>, delayMs = 0): Observable<any> {
  const polling$ = new BehaviorSubject({});
  const rePolling$ = 
    of('').pipe(
    delay(delayMs),
    tap(() => polling$.next({})),
    skip(1)
  );
  const httpPolling$ = concat(httpRequest$, rePolling$);
  return polling$.pipe(switchMap(() => httpPolling$));
}