Why is there no onComplete() rxjs operator?

Question

Why rxjs contains no onComplete operator, i.e., one that allows to do something when the source observable completes? The finalize operator works for both completion and error, while I need to only react to completion.

Yes, I know that I can use the onComplete callback of the subscribe() function, but this is something completely different. Sometimes you only want to do certain stuff on completion inside the rxjs pipeline, and not inside the subscribe call.

Am I missing something?

Answer 1

The tap operator accepts three arguments (value, error, completion)

ons$.pipe(
    tap(null, null, () => console.log("Done")),
).subscribe() 

or alternatively an observer, so you can do this:

obs$.pipe(
    tap({ complete: () => console.log("Done") })
).subscribe()

See the operator docs for more: https://rxjs-dev.firebaseapp.com/api/operators/tap

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I would recommend the observer syntax as this is the syntax that has been recommended by Ben Lesh in the past since it's more expressive.