apply a transform to each key in an object

script.js

import updateKeys from './updateKeys'
import { map, toLower } from 'ramda'

const x = {
  ONE: 1,
  TWO: 2
}

const toLowerKeys = updateKeys(toLower)
toLowerKeys(x)
// { one: 1, two: 2 }

const mapToLowerKeys = map(toLowerKeys)
mapToLowerKeys([x, x])
// [ { one: 1, two: 2 }, { one: 1, two: 2 } ]

updateKeys.js

import {
  fromPairs,
  lensIndex,
  map,
  over,
  pipe,
  toLower,
  toPairs
} from 'ramda'

const headLens = lensIndex(0)

const updateKeys = keyTransform => 
  pipe(
    toPairs,
    map(over(headLens, keyTransform)),
    fromPairs
  )

export default updateKeys

try it out