react-19

Review component architecture for React 19 best practices including size, composition, Server/Client boundaries, and anti-patterns. Use when reviewing component design.

Review React 19 performance patterns including memoization, re-renders, and bundle size. Use when reviewing performance or optimization.

Review React hook usage for React 19 compliance and best practices

Teaches component composition patterns in React 19 including children prop, compound components, and render props. Use when designing component APIs, creating reusable components, or avoiding prop drilling.

Fix React Rules of Hooks violations - conditional calls, hooks in loops/callbacks/classes

Teaches code splitting with lazy() and Suspense in React 19 for reducing initial bundle size. Use when implementing lazy loading, route-based splitting, or optimizing performance.

Teaches useOptimistic hook for immediate UI updates during async operations in React 19. Use when implementing optimistic UI patterns, instant feedback, or reducing perceived latency.

Teaches Server Actions in React 19 for form handling and data mutations. Use when implementing forms, mutations, or server-side logic. Server Actions are async functions marked with 'use server'.

Teaches when to use local state vs global state (Context) in React 19. Use when deciding state management strategy, avoiding prop drilling, or architecting component state.

Teaches when to use Server Components vs Client Components in React 19, including the 'use client' directive and boundary patterns. Use when architecting components, choosing component types, or working with Server Components.

Teaches migration from forwardRef to ref-as-prop pattern in React 19. Use when seeing forwardRef usage, upgrading React components, or when refs are mentioned. forwardRef is deprecated in React 19.

Teaches what React Compiler handles automatically in React 19, reducing need for manual memoization. Use when optimizing performance or deciding when to use useMemo/useCallback.

Teaches resource preloading APIs in React 19 including prefetchDNS, preconnect, preload, and preinit. Use when optimizing initial load or navigation performance.

Review Server Actions for security, validation, and best practices in React 19. Use when reviewing forms, mutations, or server-side logic.

Review state management patterns for React 19 best practices. Use when reviewing component state, Context usage, or state architecture.

Review React 19 test quality including coverage, patterns, and React 19 API testing. Use when reviewing tests or test coverage.

Teaches Web Components (Custom Elements) support in React 19, including property vs attribute handling and custom events. Use when integrating Web Components or working with custom HTML elements.

Teaches React Testing Library patterns for React 19 components. Use when writing component tests, testing interactions, or testing with Server Actions.

Teaches testing custom hooks in React 19 using renderHook from React Testing Library. Use when testing custom hooks or hook behavior.

Teaches testing Server Actions in isolation in React 19. Use when testing Server Actions, form handling, or server-side logic.

Teaches useFormStatus hook for tracking form submission state in React 19. Use when implementing submit buttons, form loading states, or pending indicators.

Teaches useActionState hook for managing form state with Server Actions in React 19. Use when implementing forms, handling form submissions, tracking pending states, or working with Server Functions.

Teaches Context API patterns in React 19 including use() hook for conditional context access. Use when implementing Context, avoiding prop drilling, or managing global state.

Teaches useReducer for complex state logic in React 19. Use when state updates depend on previous state, multiple related state values, or complex update logic.

React 19's use() API for reading Promises/Context conditionally. For async data fetching, Suspense, conditional context access, useContext migration.

Teaches client and server-side form validation patterns in React 19 with Server Actions. Use when implementing form validation, input checking, or error handling.