[6a3a178] | 1 | import { Observable } from '../Observable';
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| 2 | import { Operator } from '../Operator';
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| 3 | import { Subscriber } from '../Subscriber';
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| 4 | import { async } from '../scheduler/async';
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| 5 | import { MonoTypeOperatorFunction, SchedulerAction, SchedulerLike, TeardownLogic } from '../types';
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| 6 |
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| 7 | /**
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| 8 | * Emits the most recently emitted value from the source Observable within
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| 9 | * periodic time intervals.
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| 10 | *
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| 11 | * <span class="informal">Samples the source Observable at periodic time
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| 12 | * intervals, emitting what it samples.</span>
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| 13 | *
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| 14 | * ![](sampleTime.png)
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| 15 | *
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| 16 | * `sampleTime` periodically looks at the source Observable and emits whichever
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| 17 | * value it has most recently emitted since the previous sampling, unless the
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| 18 | * source has not emitted anything since the previous sampling. The sampling
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| 19 | * happens periodically in time every `period` milliseconds (or the time unit
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| 20 | * defined by the optional `scheduler` argument). The sampling starts as soon as
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| 21 | * the output Observable is subscribed.
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| 22 | *
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| 23 | * ## Example
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| 24 | * Every second, emit the most recent click at most once
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| 25 | * ```ts
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| 26 | * import { fromEvent } from 'rxjs';
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| 27 | * import { sampleTime } from 'rxjs/operators';
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| 28 | *
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| 29 | * const clicks = fromEvent(document, 'click');
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| 30 | * const result = clicks.pipe(sampleTime(1000));
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| 31 | * result.subscribe(x => console.log(x));
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| 32 | * ```
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| 33 | *
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| 34 | * @see {@link auditTime}
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| 35 | * @see {@link debounceTime}
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| 36 | * @see {@link delay}
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| 37 | * @see {@link sample}
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| 38 | * @see {@link throttleTime}
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| 39 | *
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| 40 | * @param {number} period The sampling period expressed in milliseconds or the
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| 41 | * time unit determined internally by the optional `scheduler`.
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| 42 | * @param {SchedulerLike} [scheduler=async] The {@link SchedulerLike} to use for
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| 43 | * managing the timers that handle the sampling.
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| 44 | * @return {Observable<T>} An Observable that emits the results of sampling the
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| 45 | * values emitted by the source Observable at the specified time interval.
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| 46 | * @method sampleTime
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| 47 | * @owner Observable
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| 48 | */
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| 49 | export function sampleTime<T>(period: number, scheduler: SchedulerLike = async): MonoTypeOperatorFunction<T> {
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| 50 | return (source: Observable<T>) => source.lift(new SampleTimeOperator(period, scheduler));
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| 51 | }
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| 52 |
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| 53 | class SampleTimeOperator<T> implements Operator<T, T> {
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| 54 | constructor(private period: number,
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| 55 | private scheduler: SchedulerLike) {
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| 56 | }
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| 57 |
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| 58 | call(subscriber: Subscriber<T>, source: any): TeardownLogic {
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| 59 | return source.subscribe(new SampleTimeSubscriber(subscriber, this.period, this.scheduler));
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| 60 | }
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| 61 | }
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| 62 |
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| 63 | /**
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| 64 | * We need this JSDoc comment for affecting ESDoc.
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| 65 | * @ignore
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| 66 | * @extends {Ignored}
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| 67 | */
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| 68 | class SampleTimeSubscriber<T> extends Subscriber<T> {
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| 69 | lastValue: T;
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| 70 | hasValue: boolean = false;
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| 71 |
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| 72 | constructor(destination: Subscriber<T>,
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| 73 | private period: number,
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| 74 | private scheduler: SchedulerLike) {
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| 75 | super(destination);
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| 76 | this.add(scheduler.schedule(dispatchNotification, period, { subscriber: this, period }));
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| 77 | }
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| 78 |
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| 79 | protected _next(value: T) {
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| 80 | this.lastValue = value;
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| 81 | this.hasValue = true;
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| 82 | }
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| 83 |
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| 84 | notifyNext() {
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| 85 | if (this.hasValue) {
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| 86 | this.hasValue = false;
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| 87 | this.destination.next(this.lastValue);
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| 88 | }
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| 89 | }
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| 90 | }
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| 91 |
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| 92 | function dispatchNotification<T>(this: SchedulerAction<any>, state: any) {
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| 93 | let { subscriber, period } = state;
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| 94 | subscriber.notifyNext();
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| 95 | this.schedule(state, period);
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| 96 | }
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