Observable.forkJoin() doesn't execute

forkJoin() requires all source Observables to emit at least once and to complete.

This following demo completes as expected:

const source = forkJoin(
  from([1,2,3]),
  from([9,8,7,6])
).subscribe(
  x => console.log('GOT:', x),
  err => console.log('Error:', err),
  () => console.log('Completed')
);

Live demo: https://stackblitz.com/edit/rxjs-urhkni

GOT: 3,6
Completed

Jan 2019: Updated for RxJS 6

I've faced a similar issue: I was creating a list of observables dynamically and I've noticed that forkjoin() never emits nor completes if the list of observables is empty whereas Promise.all() resolves with an empty list :

Observable.forkJoin([])
    .subscribe(() => console.log('do something here')); // This is never called

The workaround I've found is to check the length of the list and to not use this operator when it is empty.

return jobList.length ? Observable.forkJoin(jobList) : Observable.of([]);

Just add observer.complete();

Will not work:

observer.next(...)

Will work:

observer.next(...);
observer.complete();

Hope it helps.