object.entries typescript

entries.ts

type Entry<T> = [ keyof T, T[keyof T] ]
type Entries<T> = Entry<T>[]
type Key<T> = (keyof T)
type Keys<T> = Key<T>[]
type Value<T> = T[keyof T]
type Values<T> = Value<T>[]
type HasKeys<T> = { [key in keyof T]: any }

const keys = <T>(obj: T): Keys<T> => Object.keys(obj) as Keys<T>
const toEntries = <T>(obj: T): Entries<T> => Object.entries(obj) as Entries<T>
const fromEntries = <T>(entries: Entries<T>): T => Object.fromEntries(entries) as unknown as T
const mapObject = <T, U>(obj: T, callback: (entry: Entry<T>) => Entry<U>): U => fromEntries<U>(toEntries(obj).map(callback))

const a: A = {
    a: 'aaa',
    b: 'bbb'
}

const b = toEntries(a).map(([ v, k ]): Entry<A> => [ v, k + '_k' ])
const c = fromEntries<A>(b)