work.suroh.tk/node_modules/rxjs/_esm2015/operators/sample.js

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2019-12-02 12:22:45 +00:00
import { OuterSubscriber } from '../OuterSubscriber';
import { subscribeToResult } from '../util/subscribeToResult';
/**
* Emits the most recently emitted value from the source Observable whenever
* another Observable, the `notifier`, emits.
*
* <span class="informal">It's like {@link sampleTime}, but samples whenever
* the `notifier` Observable emits something.</span>
*
* <img src="./img/sample.png" width="100%">
*
* Whenever the `notifier` Observable emits a value or completes, `sample`
* looks at the source Observable and emits whichever value it has most recently
* emitted since the previous sampling, unless the source has not emitted
* anything since the previous sampling. The `notifier` is subscribed to as soon
* as the output Observable is subscribed.
*
* @example <caption>On every click, sample the most recent "seconds" timer</caption>
* var seconds = Rx.Observable.interval(1000);
* var clicks = Rx.Observable.fromEvent(document, 'click');
* var result = seconds.sample(clicks);
* result.subscribe(x => console.log(x));
*
* @see {@link audit}
* @see {@link debounce}
* @see {@link sampleTime}
* @see {@link throttle}
*
* @param {Observable<any>} notifier The Observable to use for sampling the
* source Observable.
* @return {Observable<T>} An Observable that emits the results of sampling the
* values emitted by the source Observable whenever the notifier Observable
* emits value or completes.
* @method sample
* @owner Observable
*/
export function sample(notifier) {
return (source) => source.lift(new SampleOperator(notifier));
}
class SampleOperator {
constructor(notifier) {
this.notifier = notifier;
}
call(subscriber, source) {
const sampleSubscriber = new SampleSubscriber(subscriber);
const subscription = source.subscribe(sampleSubscriber);
subscription.add(subscribeToResult(sampleSubscriber, this.notifier));
return subscription;
}
}
/**
* We need this JSDoc comment for affecting ESDoc.
* @ignore
* @extends {Ignored}
*/
class SampleSubscriber extends OuterSubscriber {
constructor() {
super(...arguments);
this.hasValue = false;
}
_next(value) {
this.value = value;
this.hasValue = true;
}
notifyNext(outerValue, innerValue, outerIndex, innerIndex, innerSub) {
this.emitValue();
}
notifyComplete() {
this.emitValue();
}
emitValue() {
if (this.hasValue) {
this.hasValue = false;
this.destination.next(this.value);
}
}
}
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