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import { mergeMap } from './mergeMap';
import { identity } from '../util/identity';
import { MonoTypeOperatorFunction, OperatorFunction, ObservableInput } from '../types';
export function mergeAll<T>(concurrent?: number): OperatorFunction<ObservableInput<T>, T>;
/**
* Converts a higher-order Observable into a first-order Observable which
* concurrently delivers all values that are emitted on the inner Observables.
*
* <span class="informal">Flattens an Observable-of-Observables.</span>
*
* ![](mergeAll.png)
*
* `mergeAll` subscribes to an Observable that emits Observables, also known as
* a higher-order Observable. Each time it observes one of these emitted inner
* Observables, it subscribes to that and delivers all the values from the
* inner Observable on the output Observable. The output Observable only
* completes once all inner Observables have completed. Any error delivered by
* a inner Observable will be immediately emitted on the output Observable.
*
* ## Examples
* Spawn a new interval Observable for each click event, and blend their outputs as one Observable
* ```javascript
* const clicks = fromEvent(document, 'click');
* const higherOrder = clicks.pipe(map((ev) => interval(1000)));
* const firstOrder = higherOrder.pipe(mergeAll());
* firstOrder.subscribe(x => console.log(x));
* ```
*
* Count from 0 to 9 every second for each click, but only allow 2 concurrent timers
* ```javascript
* const clicks = fromEvent(document, 'click');
* const higherOrder = clicks.pipe(
* map((ev) => interval(1000).pipe(take(10))),
* );
* const firstOrder = higherOrder.pipe(mergeAll(2));
* firstOrder.subscribe(x => console.log(x));
* ```
*
* @see {@link combineAll}
* @see {@link concatAll}
* @see {@link exhaust}
* @see {@link merge}
* @see {@link mergeMap}
* @see {@link mergeMapTo}
* @see {@link mergeScan}
* @see {@link switchAll}
* @see {@link switchMap}
* @see {@link zipAll}
*
* @param {number} [concurrent=Number.POSITIVE_INFINITY] Maximum number of inner
* Observables being subscribed to concurrently.
* @return {Observable} An Observable that emits values coming from all the
* inner Observables emitted by the source Observable.
* @method mergeAll
* @owner Observable
*/
export function mergeAll<T>(concurrent: number = Number.POSITIVE_INFINITY): MonoTypeOperatorFunction<T> {
return mergeMap<T, T>(identity as (value: T, index: number) => ObservableInput<T>, concurrent);
}