Back to React Fundamentals: useEffect, useState, useMemo, useCallback, useReducer

Updated for React 19.2 (2025) Over the last few years, the React ecosystem has become increasingly complex. Server Components, compilers, signals, state managers, meta-frameworks, cache layers, streaming, optimistic UI. But while everyone is chasing the next big thing, many real-world React problems still come from the same places: poorly used useEffect misunderstood dependencies unnecessary re-renders premature memoization oversized components badly distributed state This article is a return to