RxJS: Emit new value whenever all subjects emit true

Question

I have two subjects: networkStateSubject and authStateSubject.

networkStateSubject emits boolean value:

true if network connectivity is enabled,

false if network connectivity is disabled.

authStateSubject emits boolean value:

true if user logged in,

false if user logged out.

I need to combine these two subjects, so that whenever both of their values are true, new value (void) is emitted from combined observable.

score 2 · Accepted Answer · answered Apr 21 '20 at 10:35

2

You can use combineLatest and filter to check for both values.

const connectedAndAuth$ = combineLatest([networkStateSubject, authStateSubject])
   .pipe(
      filter(([isConnected, isAuth]) => isConnected && isAuth),
      map(_ => 1) //what do you mean emit a void value?
   );

answered Apr 21 '20 at 10:35

Andrei Tătar

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Perhaps you could replace `map(_ => 1)` with `mapTo(1)`? – customcommander Apr 21 '20 at 15:43
I mean type of emitted value needs to be void. e.g. Subject, Promise etc.. – Ziyaddin Sadigov Apr 21 '20 at 18:49

score 1 · Answer 2 · answered Apr 21 '20 at 10:36

1

I would use combineLatest with a selector networkStateSubject && authStateSubject, and then filter the true ones

answered Apr 21 '20 at 10:36

Krzysztof Skowronek

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RxJS: Emit new value whenever all subjects emit true

2 Answers2