useTimeout

Requirements

• Export useTimeout as a named and default React hook. Accept a callback and a non-negative finite delay in milliseconds, or null to disable scheduling. Inputs are guaranteed valid.
• Invoke the callback once after the full delay. A delay of zero remains asynchronous. The hook returns undefined.
• When the callback changes, use the latest callback without restarting the pending delay. Unrelated rerenders must not create or restart timers.
• Changing delay cancels the obsolete timeout and starts a new full delay. Setting null cancels it; changing from null schedules a new timeout.
• Clear pending timeouts on unmount and avoid duplicate invocations in React Strict Mode. No imperative reset or cancellation methods are required.
• This is a real React hook written in JS/TS, not a framework-independent timer helper. React usage examples are supplied; no HTML or CSS authoring is required.

Examples

Input: useTimeout(callback, 1000)
Output: The callback runs once after one second.

Input: Rerender at 600ms with a new callback and the same 1000ms delay.
Output: The new callback runs at the original deadline.