⚡️RxJS 🚀, mergemap with retry and fallback

retry-sub-observable.ts

public launchCachePreloading() {
    this.nomenclatureService.getUniverses().pipe(
        flatMap(e => e),
        mergeMap(universe => this.nomenclatureService.getFamilies(universe.id).pipe(
            flatMap(e => e),
            map(family => ({universeId: universe.id, familyId: family.id})),
        )),
        toArray(),
        mergeMap(families => interval(1000).pipe(
            filter(() => this.router.url === '/'),
            take(families.length),
            scan((acc) => acc + 1, -1),
            map(idx => families[idx]),
            mergeMap((e) => of(e).pipe(
                mergeMap(() => this.nomenclatureService.getProducts(e.universeId, e.familyId)),
                retry(2),
                catchError(() => EMPTY),
            )),
        ))
    ).subscribe(e => {
        console.log('val: ' + JSON.stringify(e));
    }, err => {
        console.log('err: ' + err);
    }, () => {
        console.log('finish !!!');
    });
}