| import { Operator } from '../Operator'; |
| import { Observable } from '../Observable'; |
| import { Subscriber } from '../Subscriber'; |
| import { Subscription } from '../Subscription'; |
| import { async } from '../scheduler/async'; |
| import { MonoTypeOperatorFunction, SchedulerLike, TeardownLogic } from '../types'; |
| |
| /** |
| * Emits a value from the source Observable only after a particular time span |
| * has passed without another source emission. |
| * |
| * <span class="informal">It's like {@link delay}, but passes only the most |
| * recent value from each burst of emissions.</span> |
| * |
| * ![](debounceTime.png) |
| * |
| * `debounceTime` delays values emitted by the source Observable, but drops |
| * previous pending delayed emissions if a new value arrives on the source |
| * Observable. This operator keeps track of the most recent value from the |
| * source Observable, and emits that only when `dueTime` enough time has passed |
| * without any other value appearing on the source Observable. If a new value |
| * appears before `dueTime` silence occurs, the previous value will be dropped |
| * and will not be emitted on the output Observable. |
| * |
| * This is a rate-limiting operator, because it is impossible for more than one |
| * value to be emitted in any time window of duration `dueTime`, but it is also |
| * a delay-like operator since output emissions do not occur at the same time as |
| * they did on the source Observable. Optionally takes a {@link SchedulerLike} for |
| * managing timers. |
| * |
| * ## Example |
| * Emit the most recent click after a burst of clicks |
| * ```ts |
| * import { fromEvent } from 'rxjs'; |
| * import { debounceTime } from 'rxjs/operators'; |
| * |
| * const clicks = fromEvent(document, 'click'); |
| * const result = clicks.pipe(debounceTime(1000)); |
| * result.subscribe(x => console.log(x)); |
| * ``` |
| * |
| * @see {@link auditTime} |
| * @see {@link debounce} |
| * @see {@link delay} |
| * @see {@link sampleTime} |
| * @see {@link throttleTime} |
| * |
| * @param {number} dueTime The timeout duration in milliseconds (or the time |
| * unit determined internally by the optional `scheduler`) for the window of |
| * time required to wait for emission silence before emitting the most recent |
| * source value. |
| * @param {SchedulerLike} [scheduler=async] The {@link SchedulerLike} to use for |
| * managing the timers that handle the timeout for each value. |
| * @return {Observable} An Observable that delays the emissions of the source |
| * Observable by the specified `dueTime`, and may drop some values if they occur |
| * too frequently. |
| * @method debounceTime |
| * @owner Observable |
| */ |
| export function debounceTime<T>(dueTime: number, scheduler: SchedulerLike = async): MonoTypeOperatorFunction<T> { |
| return (source: Observable<T>) => source.lift(new DebounceTimeOperator(dueTime, scheduler)); |
| } |
| |
| class DebounceTimeOperator<T> implements Operator<T, T> { |
| constructor(private dueTime: number, private scheduler: SchedulerLike) { |
| } |
| |
| call(subscriber: Subscriber<T>, source: any): TeardownLogic { |
| return source.subscribe(new DebounceTimeSubscriber(subscriber, this.dueTime, this.scheduler)); |
| } |
| } |
| |
| /** |
| * We need this JSDoc comment for affecting ESDoc. |
| * @ignore |
| * @extends {Ignored} |
| */ |
| class DebounceTimeSubscriber<T> extends Subscriber<T> { |
| private debouncedSubscription: Subscription = null; |
| private lastValue: T = null; |
| private hasValue: boolean = false; |
| |
| constructor(destination: Subscriber<T>, |
| private dueTime: number, |
| private scheduler: SchedulerLike) { |
| super(destination); |
| } |
| |
| protected _next(value: T) { |
| this.clearDebounce(); |
| this.lastValue = value; |
| this.hasValue = true; |
| this.add(this.debouncedSubscription = this.scheduler.schedule(dispatchNext, this.dueTime, this)); |
| } |
| |
| protected _complete() { |
| this.debouncedNext(); |
| this.destination.complete(); |
| } |
| |
| debouncedNext(): void { |
| this.clearDebounce(); |
| |
| if (this.hasValue) { |
| const { lastValue } = this; |
| // This must be done *before* passing the value |
| // along to the destination because it's possible for |
| // the value to synchronously re-enter this operator |
| // recursively when scheduled with things like |
| // VirtualScheduler/TestScheduler. |
| this.lastValue = null; |
| this.hasValue = false; |
| this.destination.next(lastValue); |
| } |
| } |
| |
| private clearDebounce(): void { |
| const debouncedSubscription = this.debouncedSubscription; |
| |
| if (debouncedSubscription !== null) { |
| this.remove(debouncedSubscription); |
| debouncedSubscription.unsubscribe(); |
| this.debouncedSubscription = null; |
| } |
| } |
| } |
| |
| function dispatchNext(subscriber: DebounceTimeSubscriber<any>) { |
| subscriber.debouncedNext(); |
| } |