I've already had a function working correctly.

const camelizeKeys = (obj: any): any => {
  if (Array.isArray(obj)) {
    return obj.map((v) => camelizeKeys(v)) // camelizeKeys is a function in lodash.
  } else if (obj != null && obj.constructor === Object) {
    return Object.keys(obj).reduce(
      (result, key) => ({
        ...result,
        [camelCase(key)]: camelizeKeys(obj[key])
      }),
      {}
    )
  }
  return obj
}

However, it used explicit any in the type of parameter and return value. Is it possible to express the type in a better way (e.g. infer the type of return value from the parameter type)?