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

117 lines
4.3 KiB
JavaScript

import { OuterSubscriber } from '../OuterSubscriber';
import { subscribeToResult } from '../util/subscribeToResult';
/**
* Emits a value from the source Observable only after a particular time span
* determined by another Observable has passed without another source emission.
*
* <span class="informal">It's like {@link debounceTime}, but the time span of
* emission silence is determined by a second Observable.</span>
*
* <img src="./img/debounce.png" width="100%">
*
* `debounce` 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 spawns a duration Observable by calling the
* `durationSelector` function. The value is emitted only when the duration
* Observable emits a value or completes, and if no other value was emitted on
* the source Observable since the duration Observable was spawned. If a new
* value appears before the duration Observable emits, the previous value will
* be dropped and will not be emitted on the output Observable.
*
* Like {@link debounceTime}, this is a rate-limiting operator, and also a
* delay-like operator since output emissions do not necessarily occur at the
* same time as they did on the source Observable.
*
* @example <caption>Emit the most recent click after a burst of clicks</caption>
* var clicks = Rx.Observable.fromEvent(document, 'click');
* var result = clicks.debounce(() => Rx.Observable.interval(1000));
* result.subscribe(x => console.log(x));
*
* @see {@link audit}
* @see {@link debounceTime}
* @see {@link delayWhen}
* @see {@link throttle}
*
* @param {function(value: T): SubscribableOrPromise} durationSelector A function
* that receives a value from the source Observable, for computing the timeout
* duration for each source value, returned as an Observable or a Promise.
* @return {Observable} An Observable that delays the emissions of the source
* Observable by the specified duration Observable returned by
* `durationSelector`, and may drop some values if they occur too frequently.
* @method debounce
* @owner Observable
*/
export function debounce(durationSelector) {
return (source) => source.lift(new DebounceOperator(durationSelector));
}
class DebounceOperator {
constructor(durationSelector) {
this.durationSelector = durationSelector;
}
call(subscriber, source) {
return source.subscribe(new DebounceSubscriber(subscriber, this.durationSelector));
}
}
/**
* We need this JSDoc comment for affecting ESDoc.
* @ignore
* @extends {Ignored}
*/
class DebounceSubscriber extends OuterSubscriber {
constructor(destination, durationSelector) {
super(destination);
this.durationSelector = durationSelector;
this.hasValue = false;
this.durationSubscription = null;
}
_next(value) {
try {
const result = this.durationSelector.call(this, value);
if (result) {
this._tryNext(value, result);
}
}
catch (err) {
this.destination.error(err);
}
}
_complete() {
this.emitValue();
this.destination.complete();
}
_tryNext(value, duration) {
let subscription = this.durationSubscription;
this.value = value;
this.hasValue = true;
if (subscription) {
subscription.unsubscribe();
this.remove(subscription);
}
subscription = subscribeToResult(this, duration);
if (!subscription.closed) {
this.add(this.durationSubscription = subscription);
}
}
notifyNext(outerValue, innerValue, outerIndex, innerIndex, innerSub) {
this.emitValue();
}
notifyComplete() {
this.emitValue();
}
emitValue() {
if (this.hasValue) {
const value = this.value;
const subscription = this.durationSubscription;
if (subscription) {
this.durationSubscription = null;
subscription.unsubscribe();
this.remove(subscription);
}
this.value = null;
this.hasValue = false;
super._next(value);
}
}
}
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