Real-life: throwIfEmpty() a required user

An empty stream should become an error, and catchError should return empty.

1. Solve the task in the editor — no long theory.
2. Run the check and compare your output with the expected result.
3. Stuck? Open the solution and carry the approach into your own code.

const { EMPTY, of, throwIfEmpty, catchError } = Rx;

const result$ = EMPTY.pipe(
  throwIfEmpty(),
  catchError(() => of('empty'))
);

result$.subscribe(value => console.log(value));