RxJS 6 - Do I need to unsubscribe when using first in a pipe?

Question

Given the following code

function triggerAction() {
    const asyncAction$ = of("value1");
    asyncAction$
        .clientLogin()
        .pipe(
            first(),
            tap(val => console.log(`Test: ${val}`)),
        )
        .subscribe();
}

Do I need to unsubscribe? Previously when using first with patched operators, they unsubscribed themselves once the first event was emitted, but it's not immediately clear from the documentation as to if the piped operator equivalent does the same.

https://www.learnrxjs.io/operators/filtering/first.html https://rxjs-dev.firebaseapp.com/api/operators/first

Answer 1

Both RxJS 5 and RxJS 6 versions of first work the same so you don't need to unsubscribe because it completes the chain and thus triggers dispose handlers.

If you want to be sure you can add complete callback to your tap and see if it gets called (you could add it to subscribe as well):

asyncAction$
    .clientLogin()
    .pipe(
        first(),
        tap({
            next: val => console.log(`Test: ${val}`),
            complete: () => console.log(`Complete`),
        }),
    )
    .subscribe();

Answer 2

The subscription$ will unsubscribe when the interval emits the first value. Beware, even if the AppComponent is destroyed thesubscription$ will not unsubscribe until the interval emits a value.

So it is best to make sure everything is cancelled in the ngOnDestroy hook.