Pick and/or Reject Object data by keys

pickAndReject.ts

function pick<OriginalObj extends Record<string, unknown>, Keys extends Partial<keyof OriginalObj>>(
  obj: Partial<OriginalObj>,
  keys: Keys[]
) {
  type ReturnObj = Record<Keys, OriginalObj[Keys]>;

  return keys
    .map(k => (k in obj ? { [k]: obj[k] } : {}))
    .reduce((res, o) => Object.assign(res, o), {}) as ReturnObj;
}

function reject<
  OriginalObj extends Record<string, unknown>,
  Keys extends Partial<keyof OriginalObj>
>(obj: Partial<OriginalObj>, keys: Keys[]) {
  type ReturnObj = Record<Exclude<keyof OriginalObj, Keys>, OriginalObj[Keys]>;

  return Object.keys(obj)
    .filter(k => !keys.includes(k as Keys))
    .map(k => ({ [k]: obj[k] }))
    .reduce((res, o) => Object.assign(res, o), {}) as ReturnObj;
}