How does the useMemo dependency array work?
It controls when the value recomputes. Include every value used in the computation that can change. If you miss one, the memoized value goes stale; if you include too much, it recomputes unnecessarily.
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More FAQs in useMemo in React Explained: What It Does and When to Use It
useMemo takes a function and a dependency array and returns the cached result. On subsequent renders, if the dependencies have not changed, it returns the cached value instead of recomputing, avoiding expensive work.
When a computation is expensive and would otherwise run on every render, like sorting a large list or a complex calculation. Also to keep an object or array reference stable so memoized children do not re-render unnecessarily.
No. Memoization itself costs something, so wrapping cheap computations in useMemo adds overhead without benefit. Measure first and use it only for expensive work or stable references.
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