React + TanStack Senior Developer Skill

Core Philosophy

KISS > Clever Code
Readability > Brevity  
Explicit > Implicit
Composition > Inheritance
Colocation > Separation
Type Safety > Any

Quick Decision Tree

State Management:

• Server state → TanStack Query (WAJIB)
• URL state → TanStack Router search params
• Form state → TanStack Form atau React Hook Form
• Global UI state → Zustand (bukan Redux)
• Local UI state → useState/useReducer

Routing:

• SPA → TanStack Router
• Full-stack SSR → TanStack Start
• Existing Next.js → tetap Next.js

Project Setup Workflow

1. Determine project type:

   • SPA/Client-only? → Vite + TanStack Router + Query
   • Full-stack SSR? → TanStack Start (Vinxi-based)
   • Existing project? → Incremental adoption

2. Initialize project → See folder-structure.md

3. Setup core dependencies → See recommended-libraries.md

TanStack Ecosystem References

Library	When to Read
tanstack-query.md	Data fetching, caching, mutations
tanstack-router.md	Type-safe routing, loaders, search params
tanstack-table.md	Complex tables, sorting, filtering, pagination
tanstack-form.md	Form validation, field arrays, async validation
tanstack-start.md	Full-stack SSR framework

Code Quality Standards

Naming Conventions

// Components: PascalCase dengan suffix deskriptif
UserProfileCard.tsx      // ✓
UserCard.tsx             // ✗ terlalu generic
user-profile.tsx         // ✗ wrong case

// Hooks: camelCase dengan prefix 'use'
useUserProfile()         // ✓
useGetUserProfile()      // ✗ redundant 'Get'
getUserProfile()         // ✗ missing 'use'

// Query keys: array dengan hierarchy
['users', 'list', { status }]           // ✓
['usersList']                            // ✗ tidak granular
`users-${status}`                        // ✗ string interpolation

// Files: kebab-case untuk non-components
api-client.ts            // ✓
apiClient.ts             // ✗ 

Component Structure Pattern

// 1. Imports (grouped: external → internal → types)
import { useSuspenseQuery } from '@tanstack/react-query'
import { userQueries } from '@/features/users/api'
import type { User } from '@/features/users/types'

// 2. Types (colocated, tidak di file terpisah kecuali shared)
interface UserCardProps {
  userId: string
  onSelect?: (user: User) => void
}

// 3. Component (single responsibility)
export function UserCard({ userId, onSelect }: UserCardProps) {
  // 3a. Queries/mutations first
  const { data: user } = useSuspenseQuery(userQueries.detail(userId))
  
  // 3b. Derived state (useMemo hanya jika expensive)
  const fullName = `${user.firstName} ${user.lastName}`
  
  // 3c. Handlers (useCallback hanya jika passed to memoized children)
  const handleClick = () => onSelect?.(user)
  
  // 3d. Early returns untuk edge cases
  if (!user.isActive) return null
  
  // 3e. JSX (clean, minimal nesting)
  return (
    <article onClick={handleClick} className="user-card">
      <h3>{fullName}</h3>
      <p>{user.email}</p>
    </article>
  )
}

Anti-Patterns to AVOID

// ❌ NEVER: useEffect untuk data fetching
useEffect(() => {
  fetch('/api/users').then(setUsers)
}, [])

// ✅ ALWAYS: TanStack Query
const { data: users } = useQuery(userQueries.list())

// ❌ NEVER: Prop drilling lebih dari 2 level
<Parent userData={user}>
  <Child userData={user}>
    <GrandChild userData={user} />

// ✅ ALWAYS: Context atau query di level yang butuh
function GrandChild() {
  const { data: user } = useQuery(userQueries.current())
}

// ❌ NEVER: Premature optimization
const value = useMemo(() => a + b, [a, b]) // simple math

// ✅ ALWAYS: Optimize only when measured
const value = a + b // just calculate

// ❌ NEVER: Index as key untuk dynamic lists
{items.map((item, i) => <Item key={i} />)}

// ✅ ALWAYS: Stable unique identifier
{items.map(item => <Item key={item.id} />)}

Debugging Guide

See debugging-guide.md for:

• React DevTools profiling
• TanStack Query DevTools
• Memory leak detection
• Performance bottleneck identification
• Common error patterns

Common Pitfalls & Bugs

See common-pitfalls.md for:

• Stale closure bugs
• Race conditions
• Memory leaks patterns
• Hydration mismatches
• Query invalidation mistakes

Performance Checklist

□ Bundle size < 200KB gzipped (initial)
□ Largest Contentful Paint < 2.5s
□ No unnecessary re-renders (React DevTools)
□ Images lazy loaded
□ Code splitting per route
□ Query deduplication working
□ No memory leaks (heap snapshot stable)

Code Review Checklist

□ No `any` types (use `unknown` if needed)
□ No `// @ts-ignore` tanpa penjelasan
□ Error boundaries di route level
□ Loading states handled
□ Empty states handled
□ Error states handled  
□ Accessibility (aria labels, keyboard nav)
□ No hardcoded strings (i18n ready)
□ No console.log in production code
□ Tests untuk business logic