function stable

Emits a given value if the source Observable completes without emitting any next value, otherwise mirrors the source Observable.

defaultIfEmpty<T, R>(defaultValue: R = null): OperatorFunction<T, T | R>



Optional. Default is null.

The default value used if the source Observable is empty.


OperatorFunction<T, T | R>: An Observable that emits either the specified defaultValue if the source Observable emits no items, or the values emitted by the source Observable.


If the source Observable turns out to be empty, then this operator will emit a default value.

defaultIfEmpty marble diagram

defaultIfEmpty emits the values emitted by the source Observable or a specified default value if the source Observable is empty (completes without having emitted any next value).


If no clicks happen in 5 seconds, then emit "no clicks"

import { fromEvent } from 'rxjs';
import { defaultIfEmpty, takeUntil } from 'rxjs/operators';

const clicks = fromEvent(document, 'click');
const clicksBeforeFive = clicks.pipe(takeUntil(interval(5000)));
const result = clicksBeforeFive.pipe(defaultIfEmpty('no clicks'));
result.subscribe(x => console.log(x));

See Also

© 2015–2018 Google, Inc., Netflix, Inc., Microsoft Corp. and contributors.
Code licensed under an Apache-2.0 License. Documentation licensed under CC BY 4.0.