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.

finalize<T>(callback: () => void): MonoTypeOperatorFunction<T>

Parameters

Returns

MonoTypeOperatorFunction<T>: A function that returns an Observable that mirrors the source, but will call the specified function on termination.

Description

Examples

Execute callback function when the observable completes

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

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

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

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

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

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