renameLocalStorageKey

1/**
2 * Renames a key in localStorage while preserving its value.
3 *
4 * @param oldKey - The existing key to rename.
5 * @param newKey - The new key name.
6 * @throws If the old key does not exist or the new key already exists.
7 */
8export function renameLocalStorageKey(oldKey: string, newKey: string): void {
9  if (!localStorage.getItem(oldKey)) {
10    throw new Error(`Key "${oldKey}" does not exist in localStorage`);
11  }
12  if (localStorage.getItem(newKey)) {
13    throw new Error(`Key "${newKey}" already exists in localStorage`);
14  }
15
16  const value = localStorage.getItem(oldKey);
17  localStorage.setItem(newKey, value!);
18  localStorage.removeItem(oldKey);
19}

1beforeEach(() => {
2  localStorage.clear();
3});
4
5test('renames a key while preserving its value', () => {
6  localStorage.setItem('oldKey', JSON.stringify('value'));
7
8  renameLocalStorageKey('oldKey', 'newKey');
9
10  expect(localStorage.getItem('oldKey')).toBeNull();
11  expect(localStorage.getItem('newKey')).toBe(JSON.stringify('value'));
12});
13
14test('throws if old key does not exist', () => {
15  expect(() => renameLocalStorageKey('missingKey', 'newKey')).toThrow(
16    'Key "missingKey" does not exist in localStorage'
17  );
18});
19
20test('throws if new key already exists', () => {
21  localStorage.setItem('oldKey', 'a');
22  localStorage.setItem('newKey', 'b');
23
24  expect(() => renameLocalStorageKey('oldKey', 'newKey')).toThrow(
25    'Key "newKey" already exists in localStorage'
26  );
27});