diffObjects

1/**
2 * Returns the shallow difference between two objects.
3 * For each differing key, returns a tuple [aValue, bValue].
4 *
5 * @param a - First object.
6 * @param b - Second object.
7 * @returns An object of keys with different values between a and b.
8 */
9export function diffObjects(
10  a: Record<string, any>,
11  b: Record<string, any>
12): Record<string, [any, any]> {
13  const result: Record<string, [any, any]> = {};
14
15  const keys = new Set([...Object.keys(a), ...Object.keys(b)]);
16  for (const key of keys) {
17    if (a[key] !== b[key]) {
18      result[key] = [a[key], b[key]];
19    }
20  }
21
22  return result;
23}

1test('diffObjects - detects changed values', () => {
2  const a = { name: 'Alice', age: 30 };
3  const b = { name: 'Bob', age: 30 };
4  expect(diffObjects(a, b)).toEqual({ name: ['Alice', 'Bob'] });
5});
6
7test('diffObjects - detects added keys', () => {
8  const a = { a: 1 };
9  const b = { a: 1, b: 2 };
10  expect(diffObjects(a, b)).toEqual({ b: [undefined, 2] });
11});
12
13test('diffObjects - detects removed keys', () => {
14  const a = { a: 1, b: 2 };
15  const b = { a: 1 };
16  expect(diffObjects(a, b)).toEqual({ b: [2, undefined] });
17});
18
19test('diffObjects - empty objects', () => {
20  expect(diffObjects({}, {})).toEqual({});
21});
22
23test('diffObjects - same objects', () => {
24  const obj = { x: true, y: 42 };
25  expect(diffObjects(obj, { ...obj })).toEqual({});
26});
27
28test('diffObjects - shallow comparison only', () => {
29  const a = { config: { dark: true } };
30  const b = { config: { dark: true } };
31  expect(diffObjects(a, b)).toEqual({
32    config: [{ dark: true }, { dark: true }],
33  }); // different references
34});
35