What is it

Hook that lets you memoize/cache results of calculation between renders

• only runs when one of its dependencies defined are updated

Use it when it would make a difference by preventing wasted re-renders.

Use useMemo to keep expensive, resource intensive functions from needlessly running.

const cachedValue = useMemo(calculatedValue, dependencies);

vs useCallback

useCallback is similar to useMemo, difference is that useCallback returns a memoized function whereas useMemo returns a memoized value