[6a3a178] | 1 | import { Operator } from '../Operator';
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| 2 | import { Observable } from '../Observable';
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| 3 | import { Subscriber } from '../Subscriber';
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| 4 | import { Subscription } from '../Subscription';
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| 5 | import { async } from '../scheduler/async';
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| 6 | import { MonoTypeOperatorFunction, SchedulerLike, TeardownLogic } from '../types';
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| 7 |
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| 8 | /**
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| 9 | * Emits a value from the source Observable only after a particular time span
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| 10 | * has passed without another source emission.
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| 11 | *
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| 12 | * <span class="informal">It's like {@link delay}, but passes only the most
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| 13 | * recent value from each burst of emissions.</span>
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| 14 | *
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| 15 | * ![](debounceTime.png)
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| 16 | *
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| 17 | * `debounceTime` delays values emitted by the source Observable, but drops
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| 18 | * previous pending delayed emissions if a new value arrives on the source
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| 19 | * Observable. This operator keeps track of the most recent value from the
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| 20 | * source Observable, and emits that only when `dueTime` enough time has passed
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| 21 | * without any other value appearing on the source Observable. If a new value
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| 22 | * appears before `dueTime` silence occurs, the previous value will be dropped
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| 23 | * and will not be emitted on the output Observable.
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| 24 | *
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| 25 | * This is a rate-limiting operator, because it is impossible for more than one
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| 26 | * value to be emitted in any time window of duration `dueTime`, but it is also
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| 27 | * a delay-like operator since output emissions do not occur at the same time as
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| 28 | * they did on the source Observable. Optionally takes a {@link SchedulerLike} for
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| 29 | * managing timers.
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| 30 | *
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| 31 | * ## Example
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| 32 | * Emit the most recent click after a burst of clicks
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| 33 | * ```ts
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| 34 | * import { fromEvent } from 'rxjs';
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| 35 | * import { debounceTime } from 'rxjs/operators';
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| 36 | *
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| 37 | * const clicks = fromEvent(document, 'click');
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| 38 | * const result = clicks.pipe(debounceTime(1000));
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| 39 | * result.subscribe(x => console.log(x));
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| 40 | * ```
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| 41 | *
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| 42 | * @see {@link auditTime}
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| 43 | * @see {@link debounce}
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| 44 | * @see {@link delay}
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| 45 | * @see {@link sampleTime}
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| 46 | * @see {@link throttleTime}
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| 47 | *
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| 48 | * @param {number} dueTime The timeout duration in milliseconds (or the time
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| 49 | * unit determined internally by the optional `scheduler`) for the window of
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| 50 | * time required to wait for emission silence before emitting the most recent
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| 51 | * source value.
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| 52 | * @param {SchedulerLike} [scheduler=async] The {@link SchedulerLike} to use for
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| 53 | * managing the timers that handle the timeout for each value.
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| 54 | * @return {Observable} An Observable that delays the emissions of the source
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| 55 | * Observable by the specified `dueTime`, and may drop some values if they occur
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| 56 | * too frequently.
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| 57 | * @method debounceTime
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| 58 | * @owner Observable
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| 59 | */
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| 60 | export function debounceTime<T>(dueTime: number, scheduler: SchedulerLike = async): MonoTypeOperatorFunction<T> {
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| 61 | return (source: Observable<T>) => source.lift(new DebounceTimeOperator(dueTime, scheduler));
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| 62 | }
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| 63 |
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| 64 | class DebounceTimeOperator<T> implements Operator<T, T> {
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| 65 | constructor(private dueTime: number, private scheduler: SchedulerLike) {
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| 66 | }
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| 67 |
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| 68 | call(subscriber: Subscriber<T>, source: any): TeardownLogic {
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| 69 | return source.subscribe(new DebounceTimeSubscriber(subscriber, this.dueTime, this.scheduler));
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| 70 | }
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| 71 | }
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| 72 |
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| 73 | /**
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| 74 | * We need this JSDoc comment for affecting ESDoc.
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| 75 | * @ignore
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| 76 | * @extends {Ignored}
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| 77 | */
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| 78 | class DebounceTimeSubscriber<T> extends Subscriber<T> {
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| 79 | private debouncedSubscription: Subscription = null;
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| 80 | private lastValue: T = null;
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| 81 | private hasValue: boolean = false;
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| 82 |
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| 83 | constructor(destination: Subscriber<T>,
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| 84 | private dueTime: number,
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| 85 | private scheduler: SchedulerLike) {
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| 86 | super(destination);
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| 87 | }
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| 88 |
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| 89 | protected _next(value: T) {
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| 90 | this.clearDebounce();
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| 91 | this.lastValue = value;
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| 92 | this.hasValue = true;
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| 93 | this.add(this.debouncedSubscription = this.scheduler.schedule(dispatchNext, this.dueTime, this));
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| 94 | }
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| 95 |
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| 96 | protected _complete() {
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| 97 | this.debouncedNext();
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| 98 | this.destination.complete();
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| 99 | }
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| 100 |
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| 101 | debouncedNext(): void {
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| 102 | this.clearDebounce();
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| 103 |
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| 104 | if (this.hasValue) {
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| 105 | const { lastValue } = this;
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| 106 | // This must be done *before* passing the value
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| 107 | // along to the destination because it's possible for
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| 108 | // the value to synchronously re-enter this operator
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| 109 | // recursively when scheduled with things like
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| 110 | // VirtualScheduler/TestScheduler.
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| 111 | this.lastValue = null;
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| 112 | this.hasValue = false;
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| 113 | this.destination.next(lastValue);
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| 114 | }
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| 115 | }
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| 116 |
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| 117 | private clearDebounce(): void {
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| 118 | const debouncedSubscription = this.debouncedSubscription;
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| 119 |
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| 120 | if (debouncedSubscription !== null) {
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| 121 | this.remove(debouncedSubscription);
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| 122 | debouncedSubscription.unsubscribe();
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| 123 | this.debouncedSubscription = null;
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| 124 | }
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| 125 | }
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| 126 | }
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| 127 |
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| 128 | function dispatchNext(subscriber: DebounceTimeSubscriber<any>) {
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| 129 | subscriber.debouncedNext();
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| 130 | }
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