React's useEffectEvent Hook Reads Latest Values Without Re-running Effects

React's useEffectEvent is a hook that lets an Effect read the most recent props or state without re-running when those values change. The article's example is a chat room that shows a theme-based notification on connection, where including the theme in dependencies would cause needless reconnections. Wrapping the notification logic in an Effect Event keeps the connection tied only to roomId. The hook should be called only from inside Effects, never during rendering or from event handlers, and it should not be placed in dependency arrays. It became a stable API in React 19.2, while earlier versions only offered it experimentally.