RxJS 6 conditionally pipe an observable

Question

I have an existing function which does some amount of work calling HTTP endpoints that takes care of managing some logic in my Angular component. A requirement comes in so that in a certain instance we need to all of the existing logic to be called, but also another HTTP call to be made. Below is an annotated version of my attempt.

public resolveComponent(action: string) {         //if called with no parameters, don't do anything         //otherwise, call one of the two endpoints.              let preAction = (x: any) => {             if (action === "replay") {                 return this.remediationService                            .replayRemediation(this.workflow.Id);             }             else if (action === "remove") {                 return this.remediationService                            .removeRemediation(this.workflow.Id);             }             else {                 return of([]);             }         }          this.remediationService             .resolveComponent(component)             .pipe(                 //the line below was what I added after new requirement                 mergeMap(preAction),                 mergeMap(x => {                     //grabs updated data from server                     return this.remediationService.remediationComponent(component.Id);                 })             )             .subscribe((x: SomeModel) => {                     //logic happens                 }); } 

This performs the work as expected, but is this the best way to go about conditionally chaining observables?

Answer 1

Use iif rxjs.

iif accepts a condition function and two Observables. When

• an Observable returned by the operator is subscribed, condition function will be called.

https://www.learnrxjs.io/operators/conditional/iif