biobulkbende.org/node_modules/rxjs/_esm2015/operators/debounceTime.js
2020-09-16 14:23:28 +02:00

105 lines
3.9 KiB
JavaScript

import { Subscriber } from '../Subscriber';
import { async } from '../scheduler/async';
/**
* Emits a value from the source Observable only after a particular time span
* has passed without another source emission.
*
* <span class="informal">It's like {@link delay}, but passes only the most
* recent value from each burst of emissions.</span>
*
* <img src="./img/debounceTime.png" width="100%">
*
* `debounceTime` 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 emits that only when `dueTime` enough time has passed
* without any other value appearing on the source Observable. If a new value
* appears before `dueTime` silence occurs, the previous value will be dropped
* and will not be emitted on the output Observable.
*
* This is a rate-limiting operator, because it is impossible for more than one
* value to be emitted in any time window of duration `dueTime`, but it is also
* a delay-like operator since output emissions do not occur at the same time as
* they did on the source Observable. Optionally takes a {@link IScheduler} for
* managing timers.
*
* @example <caption>Emit the most recent click after a burst of clicks</caption>
* var clicks = Rx.Observable.fromEvent(document, 'click');
* var result = clicks.debounceTime(1000);
* result.subscribe(x => console.log(x));
*
* @see {@link auditTime}
* @see {@link debounce}
* @see {@link delay}
* @see {@link sampleTime}
* @see {@link throttleTime}
*
* @param {number} dueTime The timeout duration in milliseconds (or the time
* unit determined internally by the optional `scheduler`) for the window of
* time required to wait for emission silence before emitting the most recent
* source value.
* @param {Scheduler} [scheduler=async] The {@link IScheduler} to use for
* managing the timers that handle the timeout for each value.
* @return {Observable} An Observable that delays the emissions of the source
* Observable by the specified `dueTime`, and may drop some values if they occur
* too frequently.
* @method debounceTime
* @owner Observable
*/
export function debounceTime(dueTime, scheduler = async) {
return (source) => source.lift(new DebounceTimeOperator(dueTime, scheduler));
}
class DebounceTimeOperator {
constructor(dueTime, scheduler) {
this.dueTime = dueTime;
this.scheduler = scheduler;
}
call(subscriber, source) {
return source.subscribe(new DebounceTimeSubscriber(subscriber, this.dueTime, this.scheduler));
}
}
/**
* We need this JSDoc comment for affecting ESDoc.
* @ignore
* @extends {Ignored}
*/
class DebounceTimeSubscriber extends Subscriber {
constructor(destination, dueTime, scheduler) {
super(destination);
this.dueTime = dueTime;
this.scheduler = scheduler;
this.debouncedSubscription = null;
this.lastValue = null;
this.hasValue = false;
}
_next(value) {
this.clearDebounce();
this.lastValue = value;
this.hasValue = true;
this.add(this.debouncedSubscription = this.scheduler.schedule(dispatchNext, this.dueTime, this));
}
_complete() {
this.debouncedNext();
this.destination.complete();
}
debouncedNext() {
this.clearDebounce();
if (this.hasValue) {
this.destination.next(this.lastValue);
this.lastValue = null;
this.hasValue = false;
}
}
clearDebounce() {
const debouncedSubscription = this.debouncedSubscription;
if (debouncedSubscription !== null) {
this.remove(debouncedSubscription);
debouncedSubscription.unsubscribe();
this.debouncedSubscription = null;
}
}
}
function dispatchNext(subscriber) {
subscriber.debouncedNext();
}
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