finalize

Returns an Observable that mirrors the source Observable, but will call a specified function when the source terminates on complete or error. The specified function will also be called when the subscriber explicitly unsubscribes.

Examples

Execute callback function when the observable completes

import { interval, take, finalize } from 'rxjs';

// emit value in sequence every 1 second
const source = interval(1000);
const example = source.pipe(
  take(5), //take only the first 5 values
  finalize(() => console.log('Sequence complete')) // Execute when the observable completes
);
const subscribe = example.subscribe(val => console.log(val));

// results:
// 0
// 1
// 2
// 3
// 4
// 'Sequence complete'

Execute callback function when the subscriber explicitly unsubscribes

import { interval, finalize, tap, noop, timer } from 'rxjs';

const source = interval(100).pipe(
  finalize(() => console.log('[finalize] Called')),
  tap({
    next: () => console.log('[next] Called'),
    error: () => console.log('[error] Not called'),
    complete: () => console.log('[tap complete] Not called')
  })
);

const sub = source.subscribe({
  next: x => console.log(x),
  error: noop,
  complete: () => console.log('[complete] Not called')
});

timer(150).subscribe(() => sub.unsubscribe());

// results:
// '[next] Called'
// 0
// '[finalize] Called'