React's useMemo Hook: Cache Expensive Calculations
useMemo is React's cache for expensive calculations, preventing re-computation on every render. Use it for heavy tasks like filtering large lists. The main footgun is an incomplete dependency array, which leads to stale, cached data.
useMemo is a React Hook that caches a calculation's result, preventing it from re-running on every render. Think of it as telling React, "Don't re-compute this value unless its specific inputs (dependencies) have changed." It's vital for performance when filtering large arrays or creating objects passed as props to memoized child components, preventing unnecessary re-renders. The biggest footgun is an incomplete dependency array, which causes the cached value to become stale and leads to subtle bugs.
Read the original → react.dev
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