work.suroh.tk/node_modules/rxjs/_esm5/operator/mergeScan.js

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2019-12-02 12:22:45 +00:00
/** PURE_IMPORTS_START .._operators_mergeScan PURE_IMPORTS_END */
import { mergeScan as higherOrder } from '../operators/mergeScan';
/**
* 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>
*
* @example <caption>Count the number of click events</caption>
* const click$ = Rx.Observable.fromEvent(document, 'click');
* const one$ = click$.mapTo(1);
* const seed = 0;
* const count$ = one$.mergeScan((acc, one) => Rx.Observable.of(acc + one), seed);
* count$.subscribe(x => console.log(x));
*
* // Results:
* 1
* 2
* 3
* 4
* // ...and so on for each click
*
* @param {function(acc: R, value: T): Observable<R>} accumulator
* The accumulator function called on each source value.
* @param seed The initial accumulation value.
* @param {number} [concurrent=Number.POSITIVE_INFINITY] Maximum number of
* input Observables being subscribed to concurrently.
* @return {Observable<R>} An observable of the accumulated values.
* @method mergeScan
* @owner Observable
*/
export function mergeScan(accumulator, seed, concurrent) {
if (concurrent === void 0) {
concurrent = Number.POSITIVE_INFINITY;
}
return higherOrder(accumulator, seed, concurrent)(this);
}
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