map-values.ts

const mapValues = <R, T extends { [key in K]: any }, K extends string = string>(
    hash: T,
    func: (value: T extends { [key in K]: infer V } ? V : never, key: K) => R
): { [key in K]: Exclude<R, undefined> } =>
    (Object.keys(hash) as K[]).reduce((result, key) => {
        const value = func(hash[key], key)

        if (value !== undefined) {
            result[key] = value as Exclude<R, undefined>
        }

        return result
    }, {} as { [key in K]: Exclude<R, undefined> })