move

1/**
2 * Returns a new array with an element moved from one index to another.
3 * If 'from' or 'to' is out of bounds, the original array is returned unchanged.
4 *
5 * @param arr - Source array.
6 * @param from - Index of the item to move.
7 * @param to - Target index to move the item to.
8 * @returns A new array with the element repositioned.
9 */
10export function move<T>(arr: T[], from: number, to: number): T[] {
11  if (
12    from < 0 || from >= arr.length ||
13    to < 0 || to >= arr.length ||
14    from === to
15  ) {
16    return [...arr]; // no-op or invalid
17  }
18
19  const copy = [...arr];
20  const [item] = copy.splice(from, 1);
21  copy.splice(to, 0, item);
22  return copy;
23}

1test('move - basic move forward', () => {
2  expect(move([1, 2, 3], 0, 2)).toEqual([2, 3, 1]);
3});
4
5test('move - basic move backward', () => {
6  expect(move([1, 2, 3], 2, 0)).toEqual([3, 1, 2]);
7});
8
9test('move - same index', () => {
10  expect(move([1, 2, 3], 1, 1)).toEqual([1, 2, 3]);
11});
12
13test('move - invalid indices (out of bounds)', () => {
14  expect(move([1, 2, 3], -1, 1)).toEqual([1, 2, 3]);
15  expect(move([1, 2, 3], 1, 5)).toEqual([1, 2, 3]);
16});
17
18test('move - single item array', () => {
19  expect(move([1], 0, 0)).toEqual([1]);
20});