What is useMemo, what is useeffect

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Accepted Answer

useMemo is a hook that memoizes a function's output. useEffect is a hook that runs side effects after rendering.

useMemo is used to optimize performance by caching the result of a function and returning it if the inputs haven't changed.
useEffect is used to perform side effects like fetching data or updating the DOM after rendering.
useMemo takes two arguments: a function and an array of dependencies. The function is memoized and the dependencies determine when it should be recalculated.
useEffect takes two arguments: a function and an array of dependencies. The function is run after rendering and the dependencies determine when it should be run again.
Example of useMemo: const memoizedValue = useMemo(() => expensiveFunction(a, b), [a, b])
Example of useEffect: useEffect(() => { fetchData() }, [url])

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