useEvent

Basic implementation of React RFC useEvent. It lets you define event handlers that can read the latest props/state but have always stable function identity

useEvent returns a function with a stable reference that never changes between renders, while always calling through to the latest version of your callback. This is achieved by storing the callback in a ref that is updated on every render via useIsomorphicLayoutEffect. The returned function can safely be passed as a prop or dependency without causing unnecessary re-renders or effect re-runs.

When to Use

• Passing event handlers to memoized child components (React.memo) without breaking their memoization
• Using a callback as a dependency in useEffect without triggering the effect on every render
• Any scenario where you need a stable function identity that always reads the latest closure values

Notes

• Stable identity: The returned function reference is created once via useCallback([], ...) and never changes, making it safe to omit from dependency arrays.
• Layout-phase update: The internal ref is updated during the layout phase (useIsomorphicLayoutEffect), ensuring the latest callback is available before any post-layout effects run.
• In development mode, a console error is logged if the argument is not a function.

Usage

function Demo() {
  const [count, setCount] = useState(0);

  const callbackFn = useCallback(() => {
    alert(`Current count is ${count}`);
  }, [count]);

  const memoizedFn = useEvent(() => {
    alert(`Current count is ${count}`);
  });

  return (
    <>
      <p>count: {count}</p>
      <button
        type="button"
        onClick={() => {
          setCount(c => c + 1);
        }}
      >
        Add Count
      </button>
      <div style={{ marginTop: 16 }}>
        <button type="button" onClick={callbackFn}>
          call callbackFn
        </button>
        <button type="button" onClick={memoizedFn} style={{ marginLeft: 8 }}>
          call memoizedFn
        </button>
      </div>
    </>
  );
};

API

useEvent

Returns

T

Arguments