mapKeys

const users = {
  alice: 25,
  bob: 30,
};

mapKeys(users, (value, key) => key.toUpperCase());
// {
//   ALICE: 25,
//   BOB: 30,
// }

const users = {
  alice: 25,
  bob: 30,
};

mapKeys(users, (value) => `age-${value}`);
// {
//   "age-25": 25,
//   "age-30": 30,
// }

const users = {
  alice: 25,
  bob: 30,
};

mapKeys(users, (value, key) => `${key}-${value}`);
// {
//   "alice-25": 25,
//   "bob-30": 30,
// }

const data = {
  first: 10,
  second: 20,
};

mapKeys(data, (value, key, object) => {
  return key === "first"
    ? "primary"
    : String(value + object.first);
});
// {
//   primary: 10,
//   "30": 20,
// }

const data = {
  first: "A",
  second: "B",
};

mapKeys(data, (value, key) => key === "first" ? 1 : 2);
// {
//   "1": "A",
//   "2": "B",
// }

const first = Symbol("first");
const second = Symbol("second");

const data = {
  first: "A",
  second: "B",
};

mapKeys(data, (value, key) => {
  return key === "first" ? first : second;
});

// The resulting object uses the returned symbols as keys.

const data = {
  first: 10,
  second: 20,
};

mapKeys(data, () => "value");
// {
//   value: 20,
// }

mapKeys({}, () => "key");
// {}

const data = {
  first: 10,
  second: 20,
};

const result = mapKeys(data, (value, key) => key.toUpperCase());

console.log(data);
// {
//   first: 10,
//   second: 20,
// }