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

callback

() => void

Function to be called when source terminates.

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, 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'