Interview: exhaustMap() double-submit protection

Two clicks arrive synchronously while the request is async. With exhaustMap, only the first should get through.

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 { of, timer, exhaustMap, map } = Rx;

const request = id => timer(0).pipe(map(() => 'done-' + id));

const result$ = of(1, 2).pipe(
  exhaustMap(id => request(id))
);

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