Is there any way to get the last 10 object of an observable array

Question

I'm using ngrx entity adapter selectAll. and it returns an observable list of type Object (event). I want to get only the last 10 Objects of it . this is my selector

const geteventsFeatureState = createFeatureSelector<EventState>(
  "events"
);

export const getEvents = createSelector(
  geteventsFeatureState,
  eventAdapter.getSelectors().selectAll
);

export const getEventLoading = createSelector(
  geteventsFeatureState,
  (state: EventState) => state.loading
);

export const getEventLoaded = createSelector(
  geteventsFeatureState,
  (state: EventState) => state.loaded
);

export const getError = createSelector(
  geteventsFeatureState,
  (state: EventState) => state.error
);

this is my component.ts

ngOnInit() {
    this.event$ = this.store.pipe(select(fromEvent.getEvents));
}

it's already returns all my Object and I want to select the last 10 items Anyone can help me

Answer 1

You can use selectors with props to get data based on some external conditions.In the selector we can pass props to the selector function like this:

selector.ts

  export const getLastEvents = createSelector(
      getCounterValue,
      (events, props) => events.slice(Math.max(events.length - props, 1))
    );

In component you can pass props to select method to get last 10 data.

ngOnInit() {
    this.event$ = this.store.pipe(select(fromEvent.getLastEvents,10));
}