concatMapTo.ts
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import { concatMap } from './concatMap';
import { ObservableInput, OperatorFunction, ObservedValueOf } from '../types';
/* tslint:disable:max-line-length */
export function concatMapTo<T, O extends ObservableInput<any>>(observable: O): OperatorFunction<T, ObservedValueOf<O>>;
/** @deprecated */
export function concatMapTo<T, O extends ObservableInput<any>>(observable: O, resultSelector: undefined): OperatorFunction<T, ObservedValueOf<O>>;
/** @deprecated */
export function concatMapTo<T, R, O extends ObservableInput<any>>(observable: O, resultSelector: (outerValue: T, innerValue: ObservedValueOf<O>, outerIndex: number, innerIndex: number) => R): OperatorFunction<T, R>;
/* tslint:enable:max-line-length */
/**
* Projects each source value to the same Observable which is merged multiple
* times in a serialized fashion on the output Observable.
*
* <span class="informal">It's like {@link concatMap}, but maps each value
* always to the same inner Observable.</span>
*
* 
*
* Maps each source value to the given Observable `innerObservable` regardless
* of the source value, and then flattens those resulting Observables into one
* single Observable, which is the output Observable. Each new `innerObservable`
* instance emitted on the output Observable is concatenated with the previous
* `innerObservable` instance.
*
* __Warning:__ if source values arrive endlessly and faster than their
* corresponding inner Observables can complete, it will result in memory issues
* as inner Observables amass in an unbounded buffer waiting for their turn to
* be subscribed to.
*
* Note: `concatMapTo` is equivalent to `mergeMapTo` with concurrency parameter
* set to `1`.
*
* ## Example
* For each click event, tick every second from 0 to 3, with no concurrency
* ```ts
* import { fromEvent, interval } from 'rxjs';
* import { concatMapTo, take } from 'rxjs/operators';
*
* const clicks = fromEvent(document, 'click');
* const result = clicks.pipe(
* concatMapTo(interval(1000).pipe(take(4))),
* );
* result.subscribe(x => console.log(x));
*
* // Results in the following:
* // (results are not concurrent)
* // For every click on the "document" it will emit values 0 to 3 spaced
* // on a 1000ms interval
* // one click = 1000ms-> 0 -1000ms-> 1 -1000ms-> 2 -1000ms-> 3
* ```
*
* @see {@link concat}
* @see {@link concatAll}
* @see {@link concatMap}
* @see {@link mergeMapTo}
* @see {@link switchMapTo}
*
* @param {ObservableInput} innerObservable An Observable to replace each value from
* the source Observable.
* @return {Observable} An observable of values merged together by joining the
* passed observable with itself, one after the other, for each value emitted
* from the source.
* @method concatMapTo
* @owner Observable
*/
export function concatMapTo<T, R, O extends ObservableInput<any>>(
innerObservable: O,
resultSelector?: (outerValue: T, innerValue: ObservedValueOf<O>, outerIndex: number, innerIndex: number) => R
): OperatorFunction<T, ObservedValueOf<O>|R> {
return concatMap(() => innerObservable, resultSelector);
}