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- import { Observable } from '../Observable';
- import { MonoTypeOperatorFunction, ObservableInput } from '../types';
- import { concat } from '../observable/concat';
- import { take } from './take';
- import { ignoreElements } from './ignoreElements';
- import { mapTo } from './mapTo';
- import { mergeMap } from './mergeMap';
- import { innerFrom } from '../observable/innerFrom';
- /** @deprecated The `subscriptionDelay` parameter will be removed in v8. */
- export function delayWhen<T>(
- delayDurationSelector: (value: T, index: number) => ObservableInput<any>,
- subscriptionDelay: Observable<any>
- ): MonoTypeOperatorFunction<T>;
- export function delayWhen<T>(delayDurationSelector: (value: T, index: number) => ObservableInput<any>): MonoTypeOperatorFunction<T>;
- /**
- * Delays the emission of items from the source Observable by a given time span
- * determined by the emissions of another Observable.
- *
- * <span class="informal">It's like {@link delay}, but the time span of the
- * delay duration is determined by a second Observable.</span>
- *
- * 
- *
- * `delayWhen` operator shifts each emitted value from the source Observable by
- * a time span determined by another Observable. When the source emits a value,
- * the `delayDurationSelector` function is called with the value emitted from
- * the source Observable as the first argument to the `delayDurationSelector`.
- * The `delayDurationSelector` function should return an {@link ObservableInput},
- * that is internally converted to an Observable that is called the "duration"
- * Observable.
- *
- * The source value is emitted on the output Observable only when the "duration"
- * Observable emits ({@link guide/glossary-and-semantics#next next}s) any value.
- * Upon that, the "duration" Observable gets unsubscribed.
- *
- * Before RxJS V7, the {@link guide/glossary-and-semantics#complete completion}
- * of the "duration" Observable would have been triggering the emission of the
- * source value to the output Observable, but with RxJS V7, this is not the case
- * anymore.
- *
- * Only next notifications (from the "duration" Observable) trigger values from
- * the source Observable to be passed to the output Observable. If the "duration"
- * Observable only emits the complete notification (without next), the value
- * emitted by the source Observable will never get to the output Observable - it
- * will be swallowed. If the "duration" Observable errors, the error will be
- * propagated to the output Observable.
- *
- * Optionally, `delayWhen` takes a second argument, `subscriptionDelay`, which
- * is an Observable. When `subscriptionDelay` emits its first value or
- * completes, the source Observable is subscribed to and starts behaving like
- * described in the previous paragraph. If `subscriptionDelay` is not provided,
- * `delayWhen` will subscribe to the source Observable as soon as the output
- * Observable is subscribed.
- *
- * ## Example
- *
- * Delay each click by a random amount of time, between 0 and 5 seconds
- *
- * ```ts
- * import { fromEvent, delayWhen, interval } from 'rxjs';
- *
- * const clicks = fromEvent(document, 'click');
- * const delayedClicks = clicks.pipe(
- * delayWhen(() => interval(Math.random() * 5000))
- * );
- * delayedClicks.subscribe(x => console.log(x));
- * ```
- *
- * @see {@link delay}
- * @see {@link throttle}
- * @see {@link throttleTime}
- * @see {@link debounce}
- * @see {@link debounceTime}
- * @see {@link sample}
- * @see {@link sampleTime}
- * @see {@link audit}
- * @see {@link auditTime}
- *
- * @param delayDurationSelector A function that returns an `ObservableInput` for
- * each `value` emitted by the source Observable, which is then used to delay the
- * emission of that `value` on the output Observable until the `ObservableInput`
- * returned from this function emits a next value. When called, beside `value`,
- * this function receives a zero-based `index` of the emission order.
- * @param subscriptionDelay An Observable that triggers the subscription to the
- * source Observable once it emits any value.
- * @return A function that returns an Observable that delays the emissions of
- * the source Observable by an amount of time specified by the Observable
- * returned by `delayDurationSelector`.
- */
- export function delayWhen<T>(
- delayDurationSelector: (value: T, index: number) => ObservableInput<any>,
- subscriptionDelay?: Observable<any>
- ): MonoTypeOperatorFunction<T> {
- if (subscriptionDelay) {
- // DEPRECATED PATH
- return (source: Observable<T>) =>
- concat(subscriptionDelay.pipe(take(1), ignoreElements()), source.pipe(delayWhen(delayDurationSelector)));
- }
- return mergeMap((value, index) => innerFrom(delayDurationSelector(value, index)).pipe(take(1), mapTo(value)));
- }
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