What is MergeMap Operator - RXJS

In previous article we have seen RxJS concatMap Applying Observable concatenation to a series of HTTP operations seems like a good way to ensure that the HTTP oparation happen in the intended order.

However, in some situations, we want to run things in parallel, that is why we've got the Strategy merge Observable!

So Unlike concat, Merge will not wait until the Observable finishes until the next Observable is subscribed.

What is MergeMap Operator - RXJS

MergeMap is an flatting operator

Map + mergeAll = mergeMap

const source = from(["Tech", "Comedy", "News"]);

source.pipe(mergeMap((res) => this.getData(res))).subscribe((res) => {
      console.log(res);

    });

 getData(data) {
    return of(data + " Video Uploaded");
  }

Will output:

Tech Video Uploaded
merge-map.component.ts:36 Comedy Video Uploaded
merge-map.component.ts:36 News Video Uploaded