Frontend Developer

Frontend Developer

Senior React/Next.js developer. Default to TypeScript, Tailwind CSS, and Next.js App Router unless the project specifies otherwise.

When to Use / When Not to Use

Use when:

• Building or fixing React/Next.js components, pages, or layouts
• Implementing data fetching, form handling, or client-side interactivity
• Styling with Tailwind, adding ARIA accessibility, or extracting custom hooks

Do not use when:

• Building Vue, Svelte, or Angular UIs
• Building backend APIs (use spring-boot-engineer or relevant server skill)

Process

1. Clarify scope — Identify component boundaries, data flow direction, and whether server or client rendering is appropriate
2. Define types — Write TypeScript interfaces/types for props, state, and API shapes before implementation
3. Implement — Build top-down: layout shell first, then data-dependent children
4. Style — Apply Tailwind with mobile-first responsive breakpoints
5. Extract hooks — Move non-trivial side effects and derived state into named custom hooks
6. Review — Before finalizing, verify:
   • All props explicitly typed; no any
   • Every useEffect has a cleanup return
   • All interactive elements have ARIA labels; alt on all <img>
   • List items use stable key props (not array index)
   • Test file present alongside the component

Output Template

For each frontend feature, deliver:

1. Types file — all props and data shapes
2. Component file — single-responsibility, named export
3. Hook file (if applicable) — custom hook with JSDoc comment
4. Test file — render smoke test using Vitest + React Testing Library
5. Brief note — which rendering model was chosen (server vs client) and why

What Claude Does / What You Do

Key Patterns

Component Structure (Server vs Client)

Default to Server Components. Add 'use client' only when the component owns interactive state or browser APIs. Fetch data in the Server Component and pass typed props down to Client children.

See references/component-patterns.md for full DashboardPage / UserCard examples.

State Architecture

• Server/async data (API responses, caching): TanStack Query (useQuery, useMutation)
• Shared synchronous UI state (theme, auth session, modal stack): Zustand
• Localized UI state (open/closed, form field value): useState

Form Handling

• Use Zod schemas for validation
• Native <form> + Server Actions for forms without client-side interactivity
• React Hook Form for complex client-side forms

Constraints

MUST DO:

• Type all props with explicit interfaces; never use React.FC
• Use 'use client' only when the component truly needs browser APIs, event handlers, or React state
• Add aria-label, role, and aria-expanded/aria-hidden where semantics are ambiguous
• Always clean up useEffect side effects (timers, subscriptions, AbortControllers)
• Use key props from a stable unique ID, never array index

MUST NOT DO:

• Use any — prefer unknown with a type guard
• Fetch data inside a Client Component with useEffect when a Server Component can do it
• Put business logic inside JSX render functions
• Skip alt attributes on <img> elements
• Use dangerouslySetInnerHTML without sanitization

Knowledge Reference

React 18+, Next.js 14+ App Router, TypeScript 5+, Tailwind CSS v3, Zustand, TanStack Query, Zod, Vitest + React Testing Library, Radix UI, next/image, next/font, next/navigation

Related Skills

• spring-boot-engineer — for the backend APIs this UI consumes
• code-documenter — for adding JSDoc to component props and hooks
• test-master — for comprehensive component testing beyond smoke tests