Projects each source value to the same Observable which is merged multiple times in the output Observable.

Deprecation Notes

Will be removed in v9. Use mergeMap instead: mergeMap(() => result)

mergeMapTo(innerObservable: O, concurrent?: number): OperatorFunction<unknown, ObservedValueOf<O>>

Parameters

innerObservable	O
concurrent	number	Optional. Default is undefined.

Returns

OperatorFunction<unknown, ObservedValueOf<O>>

mergeMapTo(innerObservable: O, resultSelector: (outerValue: T, innerValue: ObservedValueOf<O>, outerIndex: number, innerIndex: number) => R, concurrent?: number): OperatorFunction<T, R>

Parameters

innerObservable	O
resultSelector	(outerValue: T, innerValue: ObservedValueOf<O>, outerIndex: number, innerIndex: number) => R
concurrent	number	Optional. Default is undefined.

Returns

OperatorFunction<T, R>

Description

It's like mergeMap, but maps each value always to the same inner Observable.

Maps each source value to the given Observable innerObservable regardless of the source value, and then merges those resulting Observables into one single Observable, which is the output Observable.

Example

For each click event, start an interval Observable ticking every 1 second

import { fromEvent, mergeMapTo, interval } from 'rxjs';

const clicks = fromEvent(document, 'click');
const result = clicks.pipe(mergeMapTo(interval(1000)));

result.subscribe(x => console.log(x));

See Also

• concatMapTo
• merge
• mergeAll
• mergeMap
• mergeScan
• switchMapTo