es6/operators/throttle.js

import { OuterSubscriber } from '../OuterSubscriber';
import { subscribeToResult } from '../util/subscribeToResult';
export const defaultThrottleConfig = {
    leading: true,
    trailing: false
};
/**
 * Emits a value from the source Observable, then ignores subsequent source
 * values for a duration determined by another Observable, then repeats this
 * process.
 *
 * <span class="informal">It's like {@link throttleTime}, but the silencing
 * duration is determined by a second Observable.</span>
 *
 * <img src="./img/throttle.png" width="100%">
 *
 * `throttle` emits the source Observable values on the output Observable
 * when its internal timer is disabled, and ignores source values when the timer
 * is enabled. Initially, the timer is disabled. As soon as the first source
 * value arrives, it is forwarded to the output Observable, and then the timer
 * is enabled by calling the `durationSelector` function with the source value,
 * which returns the "duration" Observable. When the duration Observable emits a
 * value or completes, the timer is disabled, and this process repeats for the
 * next source value.
 *
 * @example <caption>Emit clicks at a rate of at most one click per second</caption>
 * var clicks = Rx.Observable.fromEvent(document, 'click');
 * var result = clicks.throttle(ev => Rx.Observable.interval(1000));
 * result.subscribe(x => console.log(x));
 *
 * @see {@link audit}
 * @see {@link debounce}
 * @see {@link delayWhen}
 * @see {@link sample}
 * @see {@link throttleTime}
 *
 * @param {function(value: T): SubscribableOrPromise} durationSelector A function
 * that receives a value from the source Observable, for computing the silencing
 * duration for each source value, returned as an Observable or a Promise.
 * @param {Object} config a configuration object to define `leading` and `trailing` behavior. Defaults
 * to `{ leading: true, trailing: false }`.
 * @return {Observable<T>} An Observable that performs the throttle operation to
 * limit the rate of emissions from the source.
 * @method throttle
 * @owner Observable
 */
export function throttle(durationSelector, config = defaultThrottleConfig) {
    return (source) => source.lift(new ThrottleOperator(durationSelector, config.leading, config.trailing));
}
class ThrottleOperator {
    constructor(durationSelector, leading, trailing) {
        this.durationSelector = durationSelector;
        this.leading = leading;
        this.trailing = trailing;
    }
    call(subscriber, source) {
        return source.subscribe(new ThrottleSubscriber(subscriber, this.durationSelector, this.leading, this.trailing));
    }
}
/**
 * We need this JSDoc comment for affecting ESDoc
 * @ignore
 * @extends {Ignored}
 */
class ThrottleSubscriber extends OuterSubscriber {
    constructor(destination, durationSelector, _leading, _trailing) {
        super(destination);
        this.destination = destination;
        this.durationSelector = durationSelector;
        this._leading = _leading;
        this._trailing = _trailing;
        this._hasTrailingValue = false;
    }
    _next(value) {
        if (this.throttled) {
            if (this._trailing) {
                this._hasTrailingValue = true;
                this._trailingValue = value;
            }
        }
        else {
            const duration = this.tryDurationSelector(value);
            if (duration) {
                this.add(this.throttled = subscribeToResult(this, duration));
            }
            if (this._leading) {
                this.destination.next(value);
                if (this._trailing) {
                    this._hasTrailingValue = true;
                    this._trailingValue = value;
                }
            }
        }
    }
    tryDurationSelector(value) {
        try {
            return this.durationSelector(value);
        }
        catch (err) {
            this.destination.error(err);
            return null;
        }
    }
    _unsubscribe() {
        const { throttled, _trailingValue, _hasTrailingValue, _trailing } = this;
        this._trailingValue = null;
        this._hasTrailingValue = false;
        if (throttled) {
            this.remove(throttled);
            this.throttled = null;
            throttled.unsubscribe();
        }
    }
    _sendTrailing() {
        const { destination, throttled, _trailing, _trailingValue, _hasTrailingValue } = this;
        if (throttled && _trailing && _hasTrailingValue) {
            destination.next(_trailingValue);
            this._trailingValue = null;
            this._hasTrailingValue = false;
        }
    }
    notifyNext(outerValue, innerValue, outerIndex, innerIndex, innerSub) {
        this._sendTrailing();
        this._unsubscribe();
    }
    notifyComplete() {
        this._sendTrailing();
        this._unsubscribe();
    }
}
//# sourceMappingURL=throttle.js.map