How to combine 2 or more observables so that you know which emitted?

Question

let's say you have 2 observables:

const obs1$: Observable<string[]> = this.getObs1$();
const obs2$: Observable<string[]> = this.getObs2$();

i want to combine these 2 so that in subscription (or rxjs map) i know which emitted the values. I can't use combineLatest because for the other observable i just get the latest value it emitted at some point.

Answer 1

There doesn't seem to be a purely RxJS solution to this (but hopefully someone can prove me wrong on that!)

You could use a variable in the outter scope to track the emitting observable as a workaround

let trigger: TriggerEnum;

const obs1$: Observable<string[]> = this.getObs1$()
  .pipe(tap(() => trigger = TriggerEnum.One));
const obs2$: Observable<string[]> = this.getObs2$()
  .pipe(tap(() => trigger = TriggerEnum.Two));;

combineLatest(....).subscribe(
 // check trigger value
);

From the docs as a just-in-case: be aware that combineLatest will not emit an initial value until each observable emits at least one value