When should you use useCallback?

When should you use useCallback?

• A. To memoize a value returned from a computation.
• B. To memoize a function so that it doesn't change unnecessarily and cause child re-renders.
• C. To create a side effect that runs after render.
• D. To create a custom hook.

Answer: (B)

Use useCallback to keep a function from changing identity on every render. It returns a memoized version of the callback that only updates when one of its dependencies changes. This is especially useful when you pass that function to child components that are memoized (for example, wrapped in React.memo) or when the function is a dependency of another effect or memoized computation. If the function identity keeps changing, those children or effects can re-render or re-run unnecessarily. Remember, useCallback is for memoizing a function, not a value—that’s useMemo. It also doesn’t create a custom hook; creating a custom hook is just writing a new function that uses hooks, whereas useCallback specifically memoizes a callback. In short, use it to stabilize function references to prevent unnecessary re-renders of consumers that depend on that function.

Use useCallback to keep a function from changing identity on every render. It returns a memoized version of the callback that only updates when one of its dependencies changes. This is especially useful when you pass that function to child components that are memoized (for example, wrapped in React.memo) or when the function is a dependency of another effect or memoized computation. If the function identity keeps changing, those children or effects can re-render or re-run unnecessarily. Remember, useCallback is for memoizing a function, not a value—that’s useMemo. It also doesn’t create a custom hook; creating a custom hook is just writing a new function that uses hooks, whereas useCallback specifically memoizes a callback. In short, use it to stabilize function references to prevent unnecessary re-renders of consumers that depend on that function.