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- import { ObservableInput, OperatorFunction } from '../types';
- /**
- * Applies an accumulator function over the source Observable where the
- * accumulator function itself returns an Observable, then each intermediate
- * Observable returned is merged into the output Observable.
- *
- * <span class="informal">It's like {@link scan}, but the Observables returned
- * by the accumulator are merged into the outer Observable.</span>
- *
- * The first parameter of the `mergeScan` is an `accumulator` function which is
- * being called every time the source Observable emits a value. `mergeScan` will
- * subscribe to the value returned by the `accumulator` function and will emit
- * values to the subscriber emitted by inner Observable.
- *
- * The `accumulator` function is being called with three parameters passed to it:
- * `acc`, `value` and `index`. The `acc` parameter is used as the state parameter
- * whose value is initially set to the `seed` parameter (the second parameter
- * passed to the `mergeScan` operator).
- *
- * `mergeScan` internally keeps the value of the `acc` parameter: as long as the
- * source Observable emits without inner Observable emitting, the `acc` will be
- * set to `seed`. The next time the inner Observable emits a value, `mergeScan`
- * will internally remember it and it will be passed to the `accumulator`
- * function as `acc` parameter the next time source emits.
- *
- * The `value` parameter of the `accumulator` function is the value emitted by the
- * source Observable, while the `index` is a number which represent the order of the
- * current emission by the source Observable. It starts with 0.
- *
- * The last parameter to the `mergeScan` is the `concurrent` value which defaults
- * to Infinity. It represents the maximum number of inner Observable subscriptions
- * at a time.
- *
- * ## Example
- *
- * Count the number of click events
- *
- * ```ts
- * import { fromEvent, map, mergeScan, of } from 'rxjs';
- *
- * const click$ = fromEvent(document, 'click');
- * const one$ = click$.pipe(map(() => 1));
- * const seed = 0;
- * const count$ = one$.pipe(
- * mergeScan((acc, one) => of(acc + one), seed)
- * );
- *
- * count$.subscribe(x => console.log(x));
- *
- * // Results:
- * // 1
- * // 2
- * // 3
- * // 4
- * // ...and so on for each click
- * ```
- *
- * @see {@link scan}
- * @see {@link switchScan}
- *
- * @param accumulator The accumulator function called on each source value.
- * @param seed The initial accumulation value.
- * @param concurrent Maximum number of input Observables being subscribed to
- * concurrently.
- * @return A function that returns an Observable of the accumulated values.
- */
- export declare function mergeScan<T, R>(accumulator: (acc: R, value: T, index: number) => ObservableInput<R>, seed: R, concurrent?: number): OperatorFunction<T, R>;
- //# sourceMappingURL=mergeScan.d.ts.map
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