filter and map array in a single loop

filterMap.ts

function filterMap<T extends unknown, R extends unknown>(
    arr: T[],
    filterFn: (item: T, index: number) => boolean,
    mapFn: (item: T, index: number) => R
) {
    return arr.reduce((acc, item, i) => {
        if (filterFn(item, i)) acc.push(mapFn(item, i));

        return acc;
    }, [] as R[]);
}