React
The skill is based on React, generated at 2026-01-31.
React is a JavaScript library for building user interfaces. It lets you compose complex UIs from small and isolated pieces of code called "components". React uses a declarative paradigm that makes it easier to reason about your application and aims to be both efficient and flexible.
Core References
| Topic | Description | Reference |
|---|---|---|
| useState | Hook for managing component state with direct updates | core-usestate |
| useEffect | Hook for synchronizing components with external systems | core-useeffect |
| useContext | Hook for reading and subscribing to context | core-usecontext |
| useRef | Hook for referencing values that don't trigger re-renders | core-useref |
| useReducer | Hook for managing complex state with a reducer function | core-usereducer |
| Suspense | Component for displaying fallback UI while content is loading | core-suspense |
| memo | Higher-order component for memoizing component renders | core-memo |
| createContext | API for creating context objects | core-createcontext |
| Fragment | Component for grouping elements without wrapper nodes | core-fragment |
| StrictMode | Component for enabling additional development checks | core-strictmode |
Features
Performance Optimization
| Topic | Description | Reference |
|---|---|---|
| useMemo | Hook for caching expensive calculations | features-usememo |
| useCallback | Hook for caching function definitions | features-usecallback |
| lazy | API for code splitting and lazy loading components | features-lazy |
| useTransition | Hook for non-blocking state updates | features-usetransition |
| useDeferredValue | Hook for deferring non-critical UI updates | features-usedeferredvalue |
| useLayoutEffect | Hook that fires synchronously before browser repaint | features-uselayouteffect |
| startTransition | API for marking non-blocking state updates | features-starttransition |
Advanced Hooks
| Topic | Description | Reference |
|---|---|---|
| useId | Hook for generating unique IDs for accessibility | features-useid |
| use | API for reading Promise and Context values | features-use |
| useActionState | Hook for managing form action state | features-useactionstate |
| useOptimistic | Hook for optimistic UI updates | features-useoptimistic |
| useInsertionEffect | Hook for CSS-in-JS libraries to inject styles | advanced-useinsertioneffect |
| useSyncExternalStore | Hook for subscribing to external stores | advanced-usesyncexternalstore |
| useImperativeHandle | Hook for customizing ref handles | advanced-useimperativehandle |
| useEffectEvent | Hook for extracting non-reactive logic from Effects | advanced-useeffectevent |
| useDebugValue | Hook for adding labels to custom hooks in DevTools | advanced-usedebugvalue |
React DOM APIs
| Topic | Description | Reference |
|---|---|---|
| createRoot | API for creating a root to render React components | react-dom-createroot |
| hydrateRoot | API for hydrating server-rendered HTML | react-dom-hydrateroot |
| createPortal | API for rendering children into different DOM nodes | react-dom-createportal |
| flushSync | API for forcing synchronous updates | react-dom-flushsync |
React Server Components
| Topic | Description | Reference |
|---|---|---|
| cache | API for caching function results in Server Components | rsc-cache |
Advanced Components
| Topic | Description | Reference |
|---|---|---|
| Profiler | Component for measuring rendering performance | advanced-profiler |
| Activity | Component for hiding and restoring UI state | features-activity |
Testing
| Topic | Description | Reference |
|---|---|---|
| act | Test helper for applying pending updates before assertions | testing-act |
Best Practices
| Topic | Description | Reference |
|---|---|---|
| Rules of Hooks | Fundamental rules for using React Hooks correctly | best-practices-rules-of-hooks |
| Component Purity | Rules for keeping React components and hooks pure | best-practices-purity |
Key Recommendations
- Use hooks at the top level - Never call hooks conditionally or in loops
- Keep components pure - Components should be idempotent and have no side effects during render
- Use useEffect for side effects - Synchronize with external systems using Effects
- Memoize expensive calculations - Use
useMemofor costly computations,useCallbackfor functions passed to memoized components - Code split with lazy - Use
lazyandSuspensefor route-based code splitting - Avoid premature optimization - Profile first, optimize only when needed
- Use React Compiler - Consider using React Compiler for automatic memoization
- Handle dependencies correctly - Always include all reactive values in Effect and memoization dependencies