mapSelector for reselect

mapSelector.ts

import { createSelector, Selector } from 'reselect'
import { isNil } from 'lodash'

export default function mapSelector<S, A, B>(
    selector: Selector<S, A>,
    mapping: (a: NonNullable<A>) => B
) {
    return createSelector(
        selector,
        value => {
            if (isNil(value)) return
            return mapping(value as NonNullable<A>)
        }
    )
}

This:

const getSomeInnerValue = createSelector(
    getSomePossiblyNilValue,
    value => value && value.someInnerValye
)

can become this:

const getSomeInnerValue = mapSelector(
    getSomePossiblyNilValue,
    value => value.someInnerValye
)