How to return value inside subscribe Angular 4

Question

I\'m new to observables in angular. I have a problem wanting to return a value inside a subscribe method. I have the following method (getFirebaseData(idForm:string):o

Answer 1

To solve this I would create a property totalQuestions$ an observable

In the TS file

totalQuestions$ = this.getFirebaseData(idForm + "/Metadatos").pipe(
  map(items => items.reduce((prev, {Total}) => prev + Total), 0)))
)

And Now in your template you can use async pipe

{{ totalQuestions$ | async }}

If you would like to use the variable in your TS file, then you can use combination operators like forkJoin or combineLatest to access this value

newVariable$ = combineLatest([totalQuestions$, ...]).pipe(
  map(([totalQuestions, ... ]) => {
    // Perform an operation here and return a value
  })
)