Is there an operator that lets me keep the initial value from a subscription after executing ,, switchMap"?

Question

I try to have access to the value emitted by the initial Observable after switchMap, inside the map operator.

https://ibb.co/1QB9zZp

I have looked at other operators, but i didn't find out any solution.

Answer 1

Here's an operator for RxJS that will emit both the outer value and inner value as an array pair [outer, inner].

Here's a switchMap() variant.

export function withSwitchMap<T, R>(inner: (T) => Observable<R>): OperatorFunction<T, [T, R]> {
    return (source: Observable<T>): Observable<[T, R]> => {
        return source.pipe(
            switchMap(a => inner(a).pipe(map(b => [a, b] as [T, R])))
        );
    }
}

Here's a mergeMap() variant.

export function withMergeMap<T, R>(inner: (T) => Observable<R>): OperatorFunction<T, [T, R]> {
    return (source: Observable<T>): Observable<[T, R]> => {
        return source.pipe(
            mergeMap(a => inner(a).pipe(map(b => [a, b] as [T, R])))
        );
    }
}