es6/operators/debounce.js

import { OuterSubscriber } from '../OuterSubscriber';
import { subscribeToResult } from '../util/subscribeToResult';
/**
 * 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>
 *
 * <img src="./img/debounce.png" width="100%">
 *
 * `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 <caption>Emit the most recent click after a burst of clicks</caption>
 * var clicks = Rx.Observable.fromEvent(document, 'click');
 * var result = clicks.debounce(() => Rx.Observable.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(durationSelector) {
    return (source) => source.lift(new DebounceOperator(durationSelector));
}
class DebounceOperator {
    constructor(durationSelector) {
        this.durationSelector = durationSelector;
    }
    call(subscriber, source) {
        return source.subscribe(new DebounceSubscriber(subscriber, this.durationSelector));
    }
}
/**
 * We need this JSDoc comment for affecting ESDoc.
 * @ignore
 * @extends {Ignored}
 */
class DebounceSubscriber extends OuterSubscriber {
    constructor(destination, durationSelector) {
        super(destination);
        this.durationSelector = durationSelector;
        this.hasValue = false;
        this.durationSubscription = null;
    }
    _next(value) {
        try {
            const result = this.durationSelector.call(this, value);
            if (result) {
                this._tryNext(value, result);
            }
        }
        catch (err) {
            this.destination.error(err);
        }
    }
    _complete() {
        this.emitValue();
        this.destination.complete();
    }
    _tryNext(value, duration) {
        let subscription = this.durationSubscription;
        this.value = value;
        this.hasValue = true;
        if (subscription) {
            subscription.unsubscribe();
            this.remove(subscription);
        }
        subscription = subscribeToResult(this, duration);
        if (!subscription.closed) {
            this.add(this.durationSubscription = subscription);
        }
    }
    notifyNext(outerValue, innerValue, outerIndex, innerIndex, innerSub) {
        this.emitValue();
    }
    notifyComplete() {
        this.emitValue();
    }
    emitValue() {
        if (this.hasValue) {
            const value = this.value;
            const subscription = this.durationSubscription;
            if (subscription) {
                this.durationSubscription = null;
                subscription.unsubscribe();
                this.remove(subscription);
            }
            this.value = null;
            this.hasValue = false;
            super._next(value);
        }
    }
}
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