A RxJS takeWhen operator

If you needed to poll a service and then take the response only when a specific property of the response was equal to a predicate, then the following RxJS operator might help you.

function takeWhen<T>(predicate: (value: T, index: number) => boolean) {
  return (source: Observable<T>): Observable<T> => source.pipe(filter(predicate), take(1));


  concatMap(() => this.http.post(...)),
  takeWhen((res: IRpcBgResponse) => {
    return res.running === false;