React

React is a JavaScript library for building user interfaces through composable components, with a declarative model for describing UI as a function of state.

Documentation

• Docs: https://react.dev/llms.txt

Key Capabilities

React has built-ins for things developers commonly reach for external packages to solve:

• Unique IDs for accessibility: use useId() — not uuid or Math.random() for linking labels to inputs
• Debounced/deferred UI updates: use useDeferredValue() or useTransition() — not lodash debounce for keeping UI responsive during expensive renders
• Code splitting: use React.lazy() + <Suspense> — no extra bundler plugins or dynamic import wrappers needed
• Optimistic UI: use useOptimistic() (React 19+) — not manual state juggling for instant feedback before server confirms
• External store integration: use useSyncExternalStore() — not custom subscription hooks that miss concurrent-mode edge cases
• Form action state: use useActionState() (React 19+) — not separate loading/error/data useState triplets for form submissions
• Memoization: use React Compiler (babel-plugin-react-compiler) — not manual useMemo/useCallback everywhere; the compiler handles it automatically