Interview: defer() a fresh factory

Each subscription should get a fresh call number.

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 { defer, of } = Rx;

let calls = 0;

const result$ = defer(() => of(++calls));

result$.subscribe(value => console.log('sub:' + value));
result$.subscribe(value => console.log('sub:' + value));