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What is the difference between useMemo and useCallback?

useMemo and useCallback are both hooks provided by React that aim to optimize performance by memoizing values or functions, respectively. However, they serve different purposes:

useMemo:

  • useMemo is used to memoize the result of a computation. It’s particularly useful when you have a computation that is expensive and you want to avoid recalculating it on every render.
  • It takes a function (the computation) and an array of dependencies. The value returned by the function will be memoized and only recalculated when one of the dependencies changes.
  • It returns the memoized value.
const memoizedValue = useMemo(() => computeExpensiveValue(a, b), [a, b]);

useCallback:

  • useCallback is used to memoize a callback function. It’s helpful when passing callbacks to child components to prevent unnecessary re-renders of those components.
  • It takes a callback function and an array of dependencies. The callback function will be memoized and only recreated when one of the dependencies changes.
  • It returns the memoized callback function.
const memoizedCallback = useCallback(() => {
  doSomething(a, b);
}, [a, b]);

In summary, useMemo is for memoizing the result of a computation, while useCallback is for memoizing a callback function. They both aim to optimize performance by preventing unnecessary recalculations or recreations.

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