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import { Operator } from '../Operator';
import { Observable } from '../Observable';
import { Subscriber } from '../Subscriber';
import { Subscription } from '../Subscription';
import { async } from '../scheduler/async';
import { MonoTypeOperatorFunction, SchedulerLike, TeardownLogic } from '../types';
* Emits a notification from the source Observable only after a particular time span
* has passed without another source emission.
* <span class="informal">It's like {@link delay}, but passes only the most
* recent notification from each burst of emissions.</span>
* ![](debounceTime.png)
* `debounceTime` delays notifications emitted by the source Observable, but drops
* previous pending delayed emissions if a new notification arrives on the source
* Observable. This operator keeps track of the most recent notification from the
* source Observable, and emits that only when `dueTime` has passed
* without any other notification appearing on the source Observable. If a new value
* appears before `dueTime` silence occurs, the previous notification will be dropped
* and will not be emitted and a new `dueTime` is scheduled.
* If the completing event happens during `dueTime` the last cached notification
* is emitted before the completion event is forwarded to the output observable.
* If the error event happens during `dueTime` or after it only the error event is
* forwarded to the output observable. The cache notification is not emitted in this case.
* This is a rate-limiting operator, because it is impossible for more than one
* notification to be emitted in any time window of duration `dueTime`, but it is also
* a delay-like operator since output emissions do not occur at the same time as
* they did on the source Observable. Optionally takes a {@link SchedulerLike} for
* managing timers.
* ## Example
* Emit the most recent click after a burst of clicks
* ```ts
* import { fromEvent } from 'rxjs';
* import { debounceTime } from 'rxjs/operators';
* const clicks = fromEvent(document, 'click');
* const result = clicks.pipe(debounceTime(1000));
* result.subscribe(x => console.log(x));
* ```
* @see {@link audit}
* @see {@link auditTime}
* @see {@link debounce}
* @see {@link debounceTime}
* @see {@link sample}
* @see {@link sampleTime}
* @see {@link throttle}
* @see {@link throttleTime}
* @param {number} dueTime The timeout duration in milliseconds (or the time
* unit determined internally by the optional `scheduler`) for the window of
* time required to wait for emission silence before emitting the most recent
* source value.
* @param {SchedulerLike} [scheduler=async] The {@link SchedulerLike} to use for
* managing the timers that handle the timeout for each value.
* @return {Observable} An Observable that delays the emissions of the source
* Observable by the specified `dueTime`, and may drop some values if they occur
* too frequently.
* @method debounceTime
* @owner Observable
export function debounceTime<T>(dueTime: number, scheduler: SchedulerLike = async): MonoTypeOperatorFunction<T> {
return (source: Observable<T>) => source.lift(new DebounceTimeOperator(dueTime, scheduler));
class DebounceTimeOperator<T> implements Operator<T, T> {
constructor(private dueTime: number, private scheduler: SchedulerLike) {
call(subscriber: Subscriber<T>, source: any): TeardownLogic {
return source.subscribe(new DebounceTimeSubscriber(subscriber, this.dueTime, this.scheduler));
* We need this JSDoc comment for affecting ESDoc.
* @ignore
* @extends {Ignored}
class DebounceTimeSubscriber<T> extends Subscriber<T> {
private debouncedSubscription: Subscription = null;
private lastValue: T = null;
private hasValue: boolean = false;
constructor(destination: Subscriber<T>,
private dueTime: number,
private scheduler: SchedulerLike) {
protected _next(value: T) {
this.lastValue = value;
this.hasValue = true;
this.add(this.debouncedSubscription = this.scheduler.schedule(dispatchNext, this.dueTime, this));
protected _complete() {
debouncedNext(): void {
if (this.hasValue) {
const { lastValue } = this;
// This must be done *before* passing the value
// along to the destination because it's possible for
// the value to synchronously re-enter this operator
// recursively when scheduled with things like
// VirtualScheduler/TestScheduler.
this.lastValue = null;
this.hasValue = false;;
private clearDebounce(): void {
const debouncedSubscription = this.debouncedSubscription;
if (debouncedSubscription !== null) {
this.debouncedSubscription = null;
function dispatchNext(subscriber: DebounceTimeSubscriber<any>) {
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