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

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2019-12-02 12:22:45 +00:00
import { OuterSubscriber } from '../OuterSubscriber';
import { subscribeToResult } from '../util/subscribeToResult';
export const defaultThrottleConfig = {
leading: true,
trailing: false
};
/**
* Emits a value from the source Observable, then ignores subsequent source
* values for a duration determined by another Observable, then repeats this
* process.
*
* <span class="informal">It's like {@link throttleTime}, but the silencing
* duration is determined by a second Observable.</span>
*
* <img src="./img/throttle.png" width="100%">
*
* `throttle` emits the source Observable values on the output Observable
* when its internal timer is disabled, and ignores source values when the timer
* is enabled. Initially, the timer is disabled. As soon as the first source
* value arrives, it is forwarded to the output Observable, and then the timer
* is enabled by calling the `durationSelector` function with the source value,
* which returns the "duration" Observable. When the duration Observable emits a
* value or completes, the timer is disabled, and this process repeats for the
* next source value.
*
* @example <caption>Emit clicks at a rate of at most one click per second</caption>
* var clicks = Rx.Observable.fromEvent(document, 'click');
* var result = clicks.throttle(ev => Rx.Observable.interval(1000));
* result.subscribe(x => console.log(x));
*
* @see {@link audit}
* @see {@link debounce}
* @see {@link delayWhen}
* @see {@link sample}
* @see {@link throttleTime}
*
* @param {function(value: T): SubscribableOrPromise} durationSelector A function
* that receives a value from the source Observable, for computing the silencing
* duration for each source value, returned as an Observable or a Promise.
* @param {Object} config a configuration object to define `leading` and `trailing` behavior. Defaults
* to `{ leading: true, trailing: false }`.
* @return {Observable<T>} An Observable that performs the throttle operation to
* limit the rate of emissions from the source.
* @method throttle
* @owner Observable
*/
export function throttle(durationSelector, config = defaultThrottleConfig) {
return (source) => source.lift(new ThrottleOperator(durationSelector, config.leading, config.trailing));
}
class ThrottleOperator {
constructor(durationSelector, leading, trailing) {
this.durationSelector = durationSelector;
this.leading = leading;
this.trailing = trailing;
}
call(subscriber, source) {
return source.subscribe(new ThrottleSubscriber(subscriber, this.durationSelector, this.leading, this.trailing));
}
}
/**
* We need this JSDoc comment for affecting ESDoc
* @ignore
* @extends {Ignored}
*/
class ThrottleSubscriber extends OuterSubscriber {
constructor(destination, durationSelector, _leading, _trailing) {
super(destination);
this.destination = destination;
this.durationSelector = durationSelector;
this._leading = _leading;
this._trailing = _trailing;
this._hasTrailingValue = false;
}
_next(value) {
if (this.throttled) {
if (this._trailing) {
this._hasTrailingValue = true;
this._trailingValue = value;
}
}
else {
const duration = this.tryDurationSelector(value);
if (duration) {
this.add(this.throttled = subscribeToResult(this, duration));
}
if (this._leading) {
this.destination.next(value);
if (this._trailing) {
this._hasTrailingValue = true;
this._trailingValue = value;
}
}
}
}
tryDurationSelector(value) {
try {
return this.durationSelector(value);
}
catch (err) {
this.destination.error(err);
return null;
}
}
/** @deprecated internal use only */ _unsubscribe() {
const { throttled, _trailingValue, _hasTrailingValue, _trailing } = this;
this._trailingValue = null;
this._hasTrailingValue = false;
if (throttled) {
this.remove(throttled);
this.throttled = null;
throttled.unsubscribe();
}
}
_sendTrailing() {
const { destination, throttled, _trailing, _trailingValue, _hasTrailingValue } = this;
if (throttled && _trailing && _hasTrailingValue) {
destination.next(_trailingValue);
this._trailingValue = null;
this._hasTrailingValue = false;
}
}
notifyNext(outerValue, innerValue, outerIndex, innerIndex, innerSub) {
this._sendTrailing();
this._unsubscribe();
}
notifyComplete() {
this._sendTrailing();
this._unsubscribe();
}
}
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