React useMemo and useCallback: When to use them and when not

Both useMemo and useCallback are React hooks that can help optimize the performance of your application by preventing unnecessary re-renders.

Here's a brief explanation of each hook:

• useMemo: This hook memoizes a value, meaning that it will only recompute the value when its dependencies change. It takes a function and an array of dependencies as inputs and returns the memoized value. This hook is useful when you have a computationally expensive function that is used as a prop for a child component, but the function is not dependent on every prop change. In this case, you can use useMemo to memoize the function so that it is only recomputed when its dependencies change.

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• useCallback: This hook memoizes a function, meaning that it will only create a new function when its dependencies change. It takes a function and an array of dependencies as inputs and returns the memoized function. This hook is useful when you have a callback function that is passed down to a child component as a prop, but the function is not dependent on every prop change. In this case, you can use useCallback to memoize the function so that it is only recreated when its dependencies change.

When to use them:

• Use useMemo when you have a computationally expensive function that is used as a prop for a child component, but the function is not dependent on every prop change.

• Use useCallback when you have a callback function that is passed down to a child component as a prop, but the function is not dependent on every prop change.

When not to use them:

• Don't use useMemo or useCallback if you don't have a computationally expensive function or callback function that needs to be memoized.

• Don't use useMemo or useCallback if the function or callback function is dependent on every prop change, as this will prevent the hook from optimizing performance.