Frontend Development Specialist
Quick Reference
Modern Frontend Development - Comprehensive patterns for React 19, Next.js 16, Vue 3.5.
Core Capabilities:
- React 19: Server components, concurrent features, cache(), Suspense
- Next.js 16: App Router, Server Actions, ISR, Route handlers
- Vue 3.5: Composition API, TypeScript, Pinia state management
- Component Architecture: Design systems, compound components, CVA
- Performance: Code splitting, dynamic imports, memoization, Framer Motion animations
When to Use:
- Modern web application development
- Component library creation
- Frontend performance optimization
- UI/UX with accessibility
Patterns
Framework Patterns
React 19 Patterns:
- Server Components, Concurrent features, cache() API, Form handling
Next.js 16 Patterns:
- App Router, Server Actions, ISR, Route Handlers, Parallel Routes
Vue 3.5 Patterns:
- Composition API, Composables, Reactivity, Pinia, Provide/Inject
Architecture Patterns
Component Architecture:
- Design tokens, CVA variants, Compound components, Accessibility
State Management:
- Zustand, Redux Toolkit, React Context, Pinia
Performance Optimization:
- Code splitting, Dynamic imports, Image optimization, Memoization
AI-Assisted Frontend Patterns:
- Visual reference strategy, Playwright verification, motion design, reasoning-level tuning
Vercel React Best Practices:
- 45 rules across 8 categories from Vercel Engineering
- Eliminating waterfalls, bundle optimization, server-side performance
- Client-side data fetching, re-render optimization, rendering performance
Implementation Quickstart
React 19 Server Component
Create an async page component that uses the cache function from React to memoize data fetching. Import Suspense for loading states. Define a getData function that fetches from the API endpoint with an id parameter and returns JSON. In the page component, wrap the DataDisplay component with Suspense using a Skeleton fallback, and pass the awaited getData result as the data prop.
Next.js Server Action
Create a server action file with the use server directive. Import revalidatePath from next/cache and z from zod for validation. Define a schema with title (minimum 1 character) and content (minimum 10 characters). The createPost function accepts FormData, validates with safeParse, returns errors on failure, creates the post in the database, and calls revalidatePath for the posts page.
Vue Composable
Create a useUser composable that accepts a userId ref parameter. Define user as a nullable ref, loading as a boolean ref, and fullName as a computed property that concatenates firstName and lastName. Use watchEffect to set loading true, fetch the user data asynchronously, assign to user ref, and set loading false. Return the user, loading, and fullName refs.
CVA Component
Import cva and VariantProps from class-variance-authority. Define buttonVariants with base classes for inline-flex, items-center, justify-center, rounded-md, and font-medium. Add variants object with variant options for default (primary background with hover) and outline (border with hover accent). Add size options for sm (h-9, px-3, text-sm), default (h-10, px-4), and lg (h-11, px-8). Set defaultVariants for variant and size. Export a Button component that applies the variants to a button element className.
Works Well With
- moai-domain-backend - Full-stack development
- moai-ref-ui-polish - Component library integration
- moai-ref-ui-polish - UI/UX design principles
.claude/rules/moai/languages/typescript.md- TypeScript patterns (auto-loaded via paths frontmatter)- moai-workflow-testing - Frontend testing
Technology Stack
Frameworks: React 19, Next.js 16, Vue 3.5, Nuxt 3
Languages: TypeScript 5.9+, JavaScript ES2024
Styling: Tailwind CSS 3.4+, CSS Modules, shadcn/ui
Animation: Framer Motion
State: Zustand, Redux Toolkit, Pinia
Testing: Vitest, Testing Library, Playwright
Verification: Playwright (visual inspection, functional testing)
Resources
Official documentation:
- React: https://react.dev/
- Next.js: https://nextjs.org/docs
- Vue: https://vuejs.org/
Version: 2.1.0
Common Rationalizations
| Rationalization | Reality |
|---|---|
| "Accessibility can be added after launch" | Post-launch accessibility is a rewrite, not an addition. Semantic HTML and ARIA are foundational, not decorative. |
| "This component is too simple to need its own test" | Simple components compose into complex UIs. A broken simple component cascades failures everywhere it is used. |
| "Server components are always faster" | Server components add network round trips. Client components with proper caching can outperform naive server components. Measure, do not assume. |
| "I will just use any as the TypeScript type for now" | any disables the type checker for everything downstream. One any infects the entire call chain. |
| "Global CSS is fine for this project" | Global CSS creates specificity conflicts as the project grows. Scoped styles (CSS modules, Tailwind) prevent collisions. |
Red Flags
- Component renders user-provided HTML without sanitization (XSS vector)
- TypeScript
anytype used in component props or state definitions - No loading or error states defined for async data fetching components
- Accessibility attributes (aria-label, role) missing from interactive elements
- Bundle size increased by more than 50KB without justification
- Component has more than 300 lines without extraction into sub-components
Verification
- All interactive elements have accessible names (aria-label or visible text)
- Components handle loading, error, and empty states
- No TypeScript
anyin new or modified code (show grep results) - Bundle size impact measured for new dependencies (show analyzer output)
- User-provided content rendered with proper escaping or sanitization
- Components under 300 lines or decomposed with clear sub-component boundaries
