invert

1/**
2 * Inverts keys and values in an object.
3 * If multiple keys share the same value, the last one will overwrite the previous.
4 *
5 * @param obj - The object to invert. Values must be string or number.
6 * @returns A new object with values as keys and keys as values.
7 */
8export function invert(obj: Record<string, string | number>): Record<string | number, string> {
9  const result: Record<string | number, string> = {};
10  for (const key in obj) {
11    result[obj[key]] = key;
12  }
13  return result;
14}

1test('invert - basic key-value inversion', () => {
2  const input = { a: 'x', b: 'y' };
3  const expected = { x: 'a', y: 'b' };
4  expect(invert(input)).toEqual(expected);
5});
6
7test('invert - numeric values as keys', () => {
8  const input = { one: 1, two: 2 };
9  const expected = { 1: 'one', 2: 'two' };
10  expect(invert(input)).toEqual(expected);
11});
12
13test('invert - same value for multiple keys (last wins)', () => {
14  const input = { a: 'x', b: 'x', c: 'y' };
15  const expected = { x: 'b', y: 'c' };
16  expect(invert(input)).toEqual(expected);
17});
18
19test('invert - empty object', () => {
20  expect(invert({})).toEqual({});
21});