FR: async map and filter for arrays with Promise predicates

[ydanneg]

FR: Would be great to have filterAsync and mapSync for arrays that work with Promise predicates.

Example (taken from internet):

async function mapAsync<T, U>(array: T[], callbackfn: (value: T, index: number, array: T[]) => Promise<U>): Promise<U[]> {
    return Promise.all(array.map(callbackfn))
}

async function filterAsync<T>(array: T[], callbackfn: (value: T, index: number, array: T[]) => Promise<boolean>): Promise<T[]> {
    const filterMap = await mapAsync(array, callbackfn)
    return array.filter((_, index) => filterMap[index])
}

[netknight]

I'll think about it, looks like such a change can lead to whole ArrayLike interface realisation with Promise result.