Effects & Selectors — Series 2

Preview — 3 of 10 questions

Why does this effect need it?

javascript

navigateAfterSave$ = createEffect(
  () => this.actions$.pipe(ofType(saveSuccess), tap(() => this.router.navigate(['/heroes']))),
  { dispatch: false },
);

ABecause effects with tap are not allowed to dispatch

BBecause dispatch: false disables the effect in production

CBecause navigation is asynchronous

DBecause the stream emits the incoming action, and without the flag NgRx would dispatch it again — an infinite loop

What does this filter?

javascript

this.actions$.pipe(ofType(loadHeroes, refreshHeroes))

AActions matching both types, which is impossible, so nothing

BOnly the first type listed

CEither action, with the emitted value typed as the union of the two — so the handler may safely read only the properties they share

DAll actions, filtered later by the effect body

The API returns the full list for the current page. Which method fits?

javascript

on(loadSuccess, (state, { heroes }) => adapter.setAll(heroes, state));       // authoritative list
on(pageSuccess, (state, { heroes }) => adapter.upsertMany(heroes, state));   // accumulate pages
on(patched,     (state, { change }) => adapter.updateOne(change, state));    // partial change

AaddMany — adds new entities and ignores existing ids

BupsertMany — inserts or fully replaces each entity, keeping everything already in the collection

CsetAll — replaces the entire collection with the response, dropping anything no longer present

DupdateMany — applies partial changes to existing entities only

Answer all 10 questions (7 more), see explanations for every answer, and track your score.