before

1/**
2 * Creates a function that allows the given callback to be called
3 * only before it reaches the specified number of invocations.
4 * Includes a .reset() method to restart the call count.
5 *
6 * @param count - Max number of allowed calls before blocking the callback.
7 * @param fn - The function to call before the threshold is reached.
8 * @returns A function with a reset() method.
9 */
10export function before(count: number, fn: () => void): (() => void) & { reset: () => void } {
11  let calls = 0;
12
13  const wrapper = () => {
14    if (calls < count) {
15      fn();
16    }
17    calls++;
18  };
19
20  wrapper.reset = () => {
21    calls = 0;
22  };
23
24  return wrapper;
25}

1test('before - allows callback only before specified count', () => {
2  const spy = jest.fn();
3  const fn = before(3, spy);
4
5  fn(); // 1
6  fn(); // 2
7  fn(); // 3 (not triggered, already reached)
8  fn(); // 4
9  expect(spy).toHaveBeenCalledTimes(2); // Only first 2 calls work
10});
11
12test('before - reset() restarts the counter', () => {
13  const spy = jest.fn();
14  const fn = before(2, spy);
15
16  fn(); // 1
17  fn(); // 2
18  expect(spy).toHaveBeenCalledTimes(1); // Only first call works
19
20  fn.reset();
21
22  fn(); // 1 again
23  fn(); // 2 again
24  expect(spy).toHaveBeenCalledTimes(2); // One more after reset
25});
26
27test('before - does nothing if count is 0 or less', () => {
28  const spy = jest.fn();
29  const fn = before(0, spy);
30
31  fn();
32  fn();
33  expect(spy).not.toHaveBeenCalled();
34});