RXJS Wait for all observables in an array to complete (or error)

Question

I\'m pushing observables into an array like such...

var tasks$ = [];
tasks$.push(Observable.timer(1000));
tasks$.push(Observable.timer(3000));
tasks$.push(Ob         


        

Answer 1

// waits for all Observables no matter of success/fails each of them
// returns array of items
// each item represent even first value of Observable or it's error
export function waitAll(args: Observable[]): Observable {
  const final = new Subject();
  const flags = new Array(args.length);
  const result = new Array(args.length);
  let total = args.length;
  for (let i = 0; i < args.length; i++) {
    flags[i] = false;
    args[i].subscribe(
      res => {
        console.info('waitAll ' + i + ' ok ', res);
        if (flags[i] === false) {
          flags[i] = true;
          result[i] = res;
          total--;
          if (total < 1) {
            final.next(result);
          }
        }
      },
      error => {
        console.error('waitAll ' + i + ' failed ', error);
        if (flags[i] === false) {
          flags[i] = true;
          result[i] = error;
          total--;
          if (total < 1) {
            final.next(result);
          }
        }
      }
    );
  }
  return final.asObservable();
}

unit test:

describe('waitAll', () => {
  it('should wait for all observables', async () => {
    const o1 = new Subject();
    const o2 = new Subject();
    const o3 = new Subject();

    const o = waitAll([o1, o2, o3]);
    const res = {arr: []};
    o.subscribe(result => res.arr = result, err => res.arr = []);

    expect(res.arr).toEqual([]);
    o1.next('success1');
    expect(res.arr).toEqual([]);
    o2.error('failed2')
    expect(res.arr).toEqual([]);
    o3.next('success3')
    expect(res.arr).toEqual(['success1', 'failed2', 'success3']);

    o1.next('success1*');
    expect(res.arr).toEqual(['success1', 'failed2', 'success3']);
    o2.error('failed2*')
    expect(res.arr).toEqual(['success1', 'failed2', 'success3']);
    o3.next('success3*')
    expect(res.arr).toEqual(['success1', 'failed2', 'success3']);
  });
});