Real-life: tap() for a debug log

First log the original value with tap, then upper-case it with map.

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, tap, map } = Rx;

const result$ = of('alpha', 'beta').pipe(
  tap(value => console.log('seen:' + value)),
  map(value => value.toUpperCase())
);

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