This method is analogous to the concatAll() operator following the merge() operator rules. So it merges all observables within an observable. It has the following signature:
As you can see, it does not receive any parameter as it will merge all observables within an observable. This behavior can be seen in the following example:
Rx.Observable.of( Rx.Observable.just(1), Rx.Observable.fromPromise(Promise.resolve(2)), Rx.Observable.of(3,4) ).mergeAll() .subscribe((k)=>console.log(k));
Now that we are using the mergeAll() operator instead of the concatAll() operator, it will follow the order of the propagated data, and as we have an Observable from a Promise, its value will be delayed ...