29 React Codebase Red Flags from a Senior Frontend Developer

A senior frontend developer at Palantir shares 29 common React codebase anti-patterns to watch for. The list covers dependency management (unnecessary libraries, heavy bundles), code organization (chaotic folder structure, junk drawer utils, barrel files), component design (god components, passing whole objects as props), state management mistakes (derived values in state, overusing global store, massive contexts), TypeScript hygiene, hooks misuse, data fetching pitfalls, error handling gaps, rendering issues (array index keys, broken memoization, nested ternaries), and maintainability problems (magic values, scattered conditionals, no abstraction over third-party libs). Each flag includes a concrete code example and a clear fix.