How to return last emitted value from observable with late subscribe

Question

Consider the following code snippet

const interval$ = Rx.Observable.interval(1000).share();

interval$.subscribe(x=> console.log('a=' + a));

setTimeout(() => {
    interval$.subscribe(x=> console.log('b=' + b));
}, 1500);

JSFIDDLE

I need the late subscriber to also return the last emitted value (which is 0 in this case). How can this be done with RxJS (Note I need a shared observable)

Answer 1

To create a shared observable that replays the last emitted value to late subscribers, replace:

const interval$ = Rx.Observable
  .interval(1000)
  .share();

with:

const interval$ = Rx.Observable
  .interval(1000)
  .publishReplay(1)
  .refCount();

share is similar to .publish().refCount() , so if you want to replay the last emitted value, publishReplay is what you could use instead.