React’s useCallback works by memoizing a function, preventing unnecessary re-creations on every render. However, since JavaScript functions form closures, useCallback captures variables from the render in which it was defined. This means if a function depends on a state or prop but is created without listing them in the dependency array, it may continue to reference outdated values even if the component updates.

For example, when a state variable is used inside useCallback but is not listed as a dependency, the function will always remember the value from the render it was created in. This can cause issues where the function does not behave as expected because it isn’t aware of the latest state.

To avoid stale closures, developers should carefully manage dependencies. Including a variable in the dependency array ensures that the function is updated whenever that variable changes. However, adding too many dependencies can cause unnecessary re-creations, reducing the effectiveness of useCallback.

In some cases, the function may not need memoization at all, especially if it is only used within a simple event handler. Overusing useCallback can lead to unnecessary complexity, so it is best used when passing functions as props to child components or optimizing performance in lists and event handlers.