export function setIsLoading<T>(callback: (isLoading: boolean) => void): MonoTypeOperatorFunction<T> {
  return source =>
    defer(() => {
      callback(true);
      return source.pipe(finalize(() => callback(false)));
    });
}

class MyComponent<T> {
  readonly isDataLoading$ = new ReplaySubject<boolean>(1);
  readonly data$ = new BehaviourSubject<T | null>(null);

  loadData(): void {
    this.service.getData().pipe(
      setIsLoading(isLoading => this.isDataLoading$.next(isLoading)),
      takeUntilDestroyed(this),
    ).subscribe(this.data$);
  }
}

const newArray = [];

for (const item of array) {
  newArray.push(item);
  
  if (item.catId === 1) {
    break;
  }
}