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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';
- export interface ThrottleConfig {
- leading?: boolean;
- trailing?: boolean;
- }
- export const defaultThrottleConfig: ThrottleConfig = {
- 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>
- *
- * 
- *
- * `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
- * Emit clicks at a rate of at most one click per second
- * ```ts
- * import { fromEvent } from 'rxjs';
- * import { throttle } from 'rxjs/operators';
- *
- * const clicks = fromEvent(document, 'click');
- * const result = clicks.pipe(throttle(ev => 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<T>(durationSelector: (value: T) => SubscribableOrPromise<any>,
- config: ThrottleConfig = defaultThrottleConfig): MonoTypeOperatorFunction<T> {
- return (source: Observable<T>) => source.lift(new ThrottleOperator(durationSelector, !!config.leading, !!config.trailing));
- }
- class ThrottleOperator<T> implements Operator<T, T> {
- constructor(private durationSelector: (value: T) => SubscribableOrPromise<any>,
- private leading: boolean,
- private trailing: boolean) {
- }
- call(subscriber: Subscriber<T>, source: any): TeardownLogic {
- 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<T, R> extends SimpleOuterSubscriber<T, R> {
- private _throttled?: Subscription;
- private _sendValue?: T;
- private _hasValue = false;
- constructor(protected destination: Subscriber<T>,
- private durationSelector: (value: T) => SubscribableOrPromise<number>,
- private _leading: boolean,
- private _trailing: boolean) {
- super(destination);
- }
- protected _next(value: T): void {
- this._hasValue = true;
- this._sendValue = value;
- if (!this._throttled) {
- if (this._leading) {
- this.send();
- } else {
- this.throttle(value);
- }
- }
- }
- private send() {
- const { _hasValue, _sendValue } = this;
- if (_hasValue) {
- this.destination.next(_sendValue);
- this.throttle(_sendValue!);
- }
- this._hasValue = false;
- this._sendValue = undefined;
- }
- private throttle(value: T): void {
- const duration = this.tryDurationSelector(value);
- if (!!duration) {
- this.add(this._throttled = innerSubscribe(duration, new SimpleInnerSubscriber(this)));
- }
- }
- private tryDurationSelector(value: T): SubscribableOrPromise<any> | null {
- try {
- return this.durationSelector(value);
- } catch (err) {
- this.destination.error(err);
- return null;
- }
- }
- private throttlingDone() {
- const { _throttled, _trailing } = this;
- if (_throttled) {
- _throttled.unsubscribe();
- }
- this._throttled = undefined;
- if (_trailing) {
- this.send();
- }
- }
- notifyNext(): void {
- this.throttlingDone();
- }
- notifyComplete(): void {
- this.throttlingDone();
- }
- }
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