normalizeCase = (mixed, clean = {}) => (
  Object
  .keys(mixed)
  .map(
    c => clean[c.toLowerCase()] =
      mixed[c] instanceof Object
      ? normalizeCase(mixed[c])
      : mixed[c]
  ),
  clean
)

console.log(normalizeCase({
  CamelCase: "Blah",
  name: "egerihor",
  props: {
    john: 4,
    PascaL: "nope"
  }
}))