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