| import { Operator } from '../Operator'; |
| import { Observable } from '../Observable'; |
| import { Subscriber } from '../Subscriber'; |
| import { Subscription } from '../Subscription'; |
| |
| import { OuterSubscriber } from '../OuterSubscriber'; |
| import { InnerSubscriber } from '../InnerSubscriber'; |
| import { subscribeToResult } from '../util/subscribeToResult'; |
| |
| import { MonoTypeOperatorFunction, SubscribableOrPromise, TeardownLogic } from '../types'; |
| |
| 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.png) |
| * |
| * `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 OuterSubscriber<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 = null; |
| } |
| |
| private throttle(value: T): void { |
| const duration = this.tryDurationSelector(value); |
| if (!!duration) { |
| this.add(this._throttled = subscribeToResult(this, duration)); |
| } |
| } |
| |
| private tryDurationSelector(value: T): SubscribableOrPromise<any> { |
| 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 = null; |
| |
| if (_trailing) { |
| this.send(); |
| } |
| } |
| |
| notifyNext(outerValue: T, innerValue: R, |
| outerIndex: number, innerIndex: number, |
| innerSub: InnerSubscriber<T, R>): void { |
| this.throttlingDone(); |
| } |
| |
| notifyComplete(): void { |
| this.throttlingDone(); |
| } |
| } |