Function listChanges

src/compat/database/list/changes.ts:8–17

(ref: DatabaseQuery, events: ChildEvent[], scheduler?: SchedulerLike)

export function listChanges<T = any>(ref: DatabaseQuery, events: ChildEvent[], scheduler?: SchedulerLike): Observable<SnapshotAction<T>[]> {
  return fromRef(ref, 'value', 'once', scheduler).pipe(
    switchMap(snapshotAction => {
      const childEvent$ = [of(snapshotAction)];
      events.forEach(event => childEvent$.push(fromRef(ref, event, 'on', scheduler)));
      return merge(...childEvent$).pipe(scan(buildView, []));
    }),
    distinctUntilChanged()
  );
}

function positionFor<T>(changes: SnapshotAction<T>[], key) {
  const len = changes.length;