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49 lines
2.4 KiB
49 lines
2.4 KiB
2 years ago
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import { Observable } from '../Observable';
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import { MonoTypeOperatorFunction } from '../interfaces';
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/**
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* Delays the emission of items from the source Observable by a given time span
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* determined by the emissions of another Observable.
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*
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* <span class="informal">It's like {@link delay}, but the time span of the
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* delay duration is determined by a second Observable.</span>
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*
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* <img src="./img/delayWhen.png" width="100%">
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*
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* `delayWhen` time shifts each emitted value from the source Observable by a
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* time span determined by another Observable. When the source emits a value,
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* the `delayDurationSelector` function is called with the source value as
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* argument, and should return an Observable, called the "duration" Observable.
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* The source value is emitted on the output Observable only when the duration
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* Observable emits a value or completes.
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*
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* Optionally, `delayWhen` takes a second argument, `subscriptionDelay`, which
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* is an Observable. When `subscriptionDelay` emits its first value or
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* completes, the source Observable is subscribed to and starts behaving like
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* described in the previous paragraph. If `subscriptionDelay` is not provided,
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* `delayWhen` will subscribe to the source Observable as soon as the output
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* Observable is subscribed.
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*
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* @example <caption>Delay each click by a random amount of time, between 0 and 5 seconds</caption>
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* var clicks = Rx.Observable.fromEvent(document, 'click');
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* var delayedClicks = clicks.delayWhen(event =>
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* Rx.Observable.interval(Math.random() * 5000)
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* );
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* delayedClicks.subscribe(x => console.log(x));
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*
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* @see {@link debounce}
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* @see {@link delay}
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*
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* @param {function(value: T): Observable} delayDurationSelector A function that
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* returns an Observable for each value emitted by the source Observable, which
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* is then used to delay the emission of that item on the output Observable
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* until the Observable returned from this function emits a value.
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* @param {Observable} subscriptionDelay An Observable that triggers the
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* subscription to the source Observable once it emits any value.
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* @return {Observable} An Observable that delays the emissions of the source
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* Observable by an amount of time specified by the Observable returned by
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* `delayDurationSelector`.
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* @method delayWhen
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* @owner Observable
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*/
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export declare function delayWhen<T>(delayDurationSelector: (value: T) => Observable<any>, subscriptionDelay?: Observable<any>): MonoTypeOperatorFunction<T>;
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