| import { Operator } from '../Operator'; |
| import { Subscriber } from '../Subscriber'; |
| import { Subscription } from '../Subscription'; |
| import { async } from '../scheduler/async'; |
| import { Observable } from '../Observable'; |
| import { ThrottleConfig, defaultThrottleConfig } from './throttle'; |
| import { MonoTypeOperatorFunction, SchedulerLike, TeardownLogic } from '../types'; |
| |
| /** |
| * Emits a value from the source Observable, then ignores subsequent source |
| * values for `duration` milliseconds, then repeats this process. |
| * |
| * <span class="informal">Lets a value pass, then ignores source values for the |
| * next `duration` milliseconds.</span> |
| * |
| * ![](throttleTime.png) |
| * |
| * `throttleTime` 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. After `duration` milliseconds (or the time unit determined |
| * internally by the optional `scheduler`) has passed, the timer is disabled, |
| * and this process repeats for the next source value. Optionally takes a |
| * {@link SchedulerLike} for managing timers. |
| * |
| * ## Examples |
| * |
| * #### Limit click rate |
| * |
| * Emit clicks at a rate of at most one click per second |
| * ```ts |
| * import { fromEvent } from 'rxjs'; |
| * import { throttleTime } from 'rxjs/operators'; |
| * |
| * const clicks = fromEvent(document, 'click'); |
| * const result = clicks.pipe(throttleTime(1000)); |
| * result.subscribe(x => console.log(x)); |
| * ``` |
| * |
| * #### Double Click |
| * |
| * The following example only emits clicks which happen within a subsequent |
| * delay of 400ms of the previous click. This for example can emulate a double |
| * click. It makes use of the `trailing` parameter of the throttle configuration. |
| * |
| * ```ts |
| * import { fromEvent, asyncScheduler } from 'rxjs'; |
| * import { throttleTime, withLatestFrom } from 'rxjs/operators'; |
| * |
| * // defaultThottleConfig = { leading: true, trailing: false } |
| * const throttleConfig = { |
| * leading: false, |
| * trailing: true |
| * } |
| * |
| * const click = fromEvent(document, 'click'); |
| * const doubleClick = click.pipe( |
| * throttleTime(400, asyncScheduler, throttleConfig) |
| * ); |
| * |
| * doubleClick.subscribe((throttleValue: Event) => { |
| * console.log(`Double-clicked! Timestamp: ${throttleValue.timeStamp}`); |
| * }); |
| * ``` |
| * |
| * If you enable the `leading` parameter in this example, the output would be the primary click and |
| * the double click, but restricts additional clicks within 400ms. |
| * |
| * @see {@link auditTime} |
| * @see {@link debounceTime} |
| * @see {@link delay} |
| * @see {@link sampleTime} |
| * @see {@link throttle} |
| * |
| * @param {number} duration Time to wait before emitting another value after |
| * emitting the last value, measured in milliseconds or the time unit determined |
| * internally by the optional `scheduler`. |
| * @param {SchedulerLike} [scheduler=async] The {@link SchedulerLike} to use for |
| * managing the timers that handle the throttling. |
| * @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 throttleTime |
| * @owner Observable |
| */ |
| export function throttleTime<T>(duration: number, |
| scheduler: SchedulerLike = async, |
| config: ThrottleConfig = defaultThrottleConfig): MonoTypeOperatorFunction<T> { |
| return (source: Observable<T>) => source.lift(new ThrottleTimeOperator(duration, scheduler, config.leading, config.trailing)); |
| } |
| |
| class ThrottleTimeOperator<T> implements Operator<T, T> { |
| constructor(private duration: number, |
| private scheduler: SchedulerLike, |
| private leading: boolean, |
| private trailing: boolean) { |
| } |
| |
| call(subscriber: Subscriber<T>, source: any): TeardownLogic { |
| return source.subscribe( |
| new ThrottleTimeSubscriber(subscriber, this.duration, this.scheduler, this.leading, this.trailing) |
| ); |
| } |
| } |
| |
| /** |
| * We need this JSDoc comment for affecting ESDoc. |
| * @ignore |
| * @extends {Ignored} |
| */ |
| class ThrottleTimeSubscriber<T> extends Subscriber<T> { |
| private throttled: Subscription; |
| private _hasTrailingValue: boolean = false; |
| private _trailingValue: T = null; |
| |
| constructor(destination: Subscriber<T>, |
| private duration: number, |
| private scheduler: SchedulerLike, |
| private leading: boolean, |
| private trailing: boolean) { |
| super(destination); |
| } |
| |
| protected _next(value: T) { |
| if (this.throttled) { |
| if (this.trailing) { |
| this._trailingValue = value; |
| this._hasTrailingValue = true; |
| } |
| } else { |
| this.add(this.throttled = this.scheduler.schedule<DispatchArg<T>>(dispatchNext, this.duration, { subscriber: this })); |
| if (this.leading) { |
| this.destination.next(value); |
| } else if (this.trailing) { |
| this._trailingValue = value; |
| this._hasTrailingValue = true; |
| } |
| } |
| } |
| |
| protected _complete() { |
| if (this._hasTrailingValue) { |
| this.destination.next(this._trailingValue); |
| this.destination.complete(); |
| } else { |
| this.destination.complete(); |
| } |
| } |
| |
| clearThrottle() { |
| const throttled = this.throttled; |
| if (throttled) { |
| if (this.trailing && this._hasTrailingValue) { |
| this.destination.next(this._trailingValue); |
| this._trailingValue = null; |
| this._hasTrailingValue = false; |
| } |
| throttled.unsubscribe(); |
| this.remove(throttled); |
| this.throttled = null; |
| } |
| } |
| } |
| |
| interface DispatchArg<T> { |
| subscriber: ThrottleTimeSubscriber<T>; |
| } |
| |
| function dispatchNext<T>(arg: DispatchArg<T>) { |
| const { subscriber } = arg; |
| subscriber.clearThrottle(); |
| } |