rxjs-1

index.mjs

// @ts-check

import { Observable, of, from, reduce, mergeMap } from 'rxjs'

type IObjectNode = { value: number };

const arr1 = new Observable<IObjectNode[]>(subscriber => {
  setInterval(() => {
    subscriber.next([
      createObjectNode(),
      createObjectNode()
    ]);
  }, 1000);
});

const arr2 = arr1.pipe(mergeMap((obj) => {
  if (whatif(obj)) {
    return of(obj);
  }

  return f(obj).pipe(reduce((acc, it) => {
    acc.push(it);
    return acc;
  }, [] as IObjectNode[]));
}));

arr2.subscribe(console.log);

function createObjectNode(): IObjectNode {
  const uuid = Math.random();
  return { value: uuid };
}

function f(x: IObjectNode[]): Observable<IObjectNode> {
  return from(x);
}

function whatif(ob: IObjectNode[]) {
  // @ts-ignore
  whatif.i ??= 0;
  // @ts-ignore
  whatif.i++;
  // @ts-ignore
  return whatif.i % 2;
}