How to return data or make two more requests in Rx.js depending on the result of the first request?

Question

JavaScript

I need to make a request via HttpClient (Angular) After the response comes, I need to return the data if the email does not exist in the database, and if it does, then transfer the stream to two more requests and return the already processed result of these two requests to the subscript callback (Observables since httpClient I use).

Answer 1

This is done via switchMap:

this.httpClient.get('/check-email').pipe(
  switchMap(emailResult => {
    if (emailResult !== exists) {
      return of(dataForNonExistingEmail);
    }
    
    return forkJoin(
      this.httpClient.get('/user-data1'),
      this.httpClient.get('/user-data2')
    );
  })
)