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- import { Operator } from '../Operator';
- import { Observable } from '../Observable';
- import { Subscriber } from '../Subscriber';
- import { Subscription } from '../Subscription';
- import { MonoTypeOperatorFunction, SubscribableOrPromise, TeardownLogic } from '../types';
- import { SimpleOuterSubscriber, innerSubscribe, SimpleInnerSubscriber } from '../innerSubscribe';
- /**
- * Emits a value from the source Observable only after a particular time span
- * determined by another Observable has passed without another source emission.
- *
- * <span class="informal">It's like {@link debounceTime}, but the time span of
- * emission silence is determined by a second Observable.</span>
- *
- * 
- *
- * `debounce` delays values emitted by the source Observable, but drops previous
- * pending delayed emissions if a new value arrives on the source Observable.
- * This operator keeps track of the most recent value from the source
- * Observable, and spawns a duration Observable by calling the
- * `durationSelector` function. The value is emitted only when the duration
- * Observable emits a value or completes, and if no other value was emitted on
- * the source Observable since the duration Observable was spawned. If a new
- * value appears before the duration Observable emits, the previous value will
- * be dropped and will not be emitted on the output Observable.
- *
- * Like {@link debounceTime}, this is a rate-limiting operator, and also a
- * delay-like operator since output emissions do not necessarily occur at the
- * same time as they did on the source Observable.
- *
- * ## Example
- * Emit the most recent click after a burst of clicks
- * ```ts
- * import { fromEvent, interval } from 'rxjs';
- * import { debounce } from 'rxjs/operators';
- *
- * const clicks = fromEvent(document, 'click');
- * const result = clicks.pipe(debounce(() => interval(1000)));
- * result.subscribe(x => console.log(x));
- * ```
- *
- * @see {@link audit}
- * @see {@link debounceTime}
- * @see {@link delayWhen}
- * @see {@link throttle}
- *
- * @param {function(value: T): SubscribableOrPromise} durationSelector A function
- * that receives a value from the source Observable, for computing the timeout
- * duration for each source value, returned as an Observable or a Promise.
- * @return {Observable} An Observable that delays the emissions of the source
- * Observable by the specified duration Observable returned by
- * `durationSelector`, and may drop some values if they occur too frequently.
- * @method debounce
- * @owner Observable
- */
- export function debounce<T>(durationSelector: (value: T) => SubscribableOrPromise<any>): MonoTypeOperatorFunction<T> {
- return (source: Observable<T>) => source.lift(new DebounceOperator(durationSelector));
- }
- class DebounceOperator<T> implements Operator<T, T> {
- constructor(private durationSelector: (value: T) => SubscribableOrPromise<any>) {
- }
- call(subscriber: Subscriber<T>, source: any): TeardownLogic {
- return source.subscribe(new DebounceSubscriber(subscriber, this.durationSelector));
- }
- }
- /**
- * We need this JSDoc comment for affecting ESDoc.
- * @ignore
- * @extends {Ignored}
- */
- class DebounceSubscriber<T, R> extends SimpleOuterSubscriber<T, R> {
- private value?: T;
- private hasValue = false;
- private durationSubscription?: Subscription;
- constructor(destination: Subscriber<R>,
- private durationSelector: (value: T) => SubscribableOrPromise<any>) {
- super(destination);
- }
- protected _next(value: T): void {
- try {
- const result = this.durationSelector.call(this, value);
- if (result) {
- this._tryNext(value, result);
- }
- } catch (err) {
- this.destination.error!(err);
- }
- }
- protected _complete(): void {
- this.emitValue();
- this.destination.complete!();
- }
- private _tryNext(value: T, duration: SubscribableOrPromise<any>): void {
- let subscription = this.durationSubscription;
- this.value = value;
- this.hasValue = true;
- if (subscription) {
- subscription.unsubscribe();
- this.remove(subscription);
- }
- subscription = innerSubscribe(duration, new SimpleInnerSubscriber(this));
- if (subscription && !subscription.closed) {
- this.add(this.durationSubscription = subscription);
- }
- }
- notifyNext(): void {
- this.emitValue();
- }
- notifyComplete(): void {
- this.emitValue();
- }
- emitValue(): void {
- if (this.hasValue) {
- const value = this.value;
- const subscription = this.durationSubscription;
- if (subscription) {
- this.durationSubscription = undefined;
- subscription.unsubscribe();
- this.remove(subscription);
- }
- // 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 if the duration selector Observable
- // emits synchronously
- this.value = undefined;
- this.hasValue = false;
- super._next(value!);
- }
- }
- }
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