78 lines
2.6 KiB
JavaScript
78 lines
2.6 KiB
JavaScript
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import { OuterSubscriber } from '../OuterSubscriber';
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import { subscribeToResult } from '../util/subscribeToResult';
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/**
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* Emits the most recently emitted value from the source Observable whenever
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* another Observable, the `notifier`, emits.
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*
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* <span class="informal">It's like {@link sampleTime}, but samples whenever
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* the `notifier` Observable emits something.</span>
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*
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* <img src="./img/sample.png" width="100%">
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*
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* Whenever the `notifier` Observable emits a value or completes, `sample`
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* looks at the source Observable and emits whichever value it has most recently
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* emitted since the previous sampling, unless the source has not emitted
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* anything since the previous sampling. The `notifier` is subscribed to as soon
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* as the output Observable is subscribed.
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*
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* @example <caption>On every click, sample the most recent "seconds" timer</caption>
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* var seconds = Rx.Observable.interval(1000);
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* var clicks = Rx.Observable.fromEvent(document, 'click');
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* var result = seconds.sample(clicks);
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* result.subscribe(x => console.log(x));
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*
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* @see {@link audit}
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* @see {@link debounce}
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* @see {@link sampleTime}
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* @see {@link throttle}
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*
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* @param {Observable<any>} notifier The Observable to use for sampling the
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* source Observable.
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* @return {Observable<T>} An Observable that emits the results of sampling the
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* values emitted by the source Observable whenever the notifier Observable
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* emits value or completes.
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* @method sample
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* @owner Observable
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*/
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export function sample(notifier) {
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return (source) => source.lift(new SampleOperator(notifier));
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}
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class SampleOperator {
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constructor(notifier) {
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this.notifier = notifier;
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}
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call(subscriber, source) {
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const sampleSubscriber = new SampleSubscriber(subscriber);
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const subscription = source.subscribe(sampleSubscriber);
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subscription.add(subscribeToResult(sampleSubscriber, this.notifier));
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return subscription;
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}
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}
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/**
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* We need this JSDoc comment for affecting ESDoc.
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* @ignore
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* @extends {Ignored}
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*/
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class SampleSubscriber extends OuterSubscriber {
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constructor() {
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super(...arguments);
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this.hasValue = false;
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}
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_next(value) {
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this.value = value;
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this.hasValue = true;
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}
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notifyNext(outerValue, innerValue, outerIndex, innerIndex, innerSub) {
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this.emitValue();
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}
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notifyComplete() {
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this.emitValue();
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}
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emitValue() {
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if (this.hasValue) {
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this.hasValue = false;
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this.destination.next(this.value);
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}
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}
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}
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//# sourceMappingURL=sample.js.map
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