TypeScript Rules

Version: TypeScript 5.9+

Tooling

• Linting: ESLint 9 flat config or Biome
• Formatting: Prettier or Biome
• Testing: Vitest (recommended) or Jest
• Package management: pnpm (recommended) or npm

Best Practices (2026)

• Enable strict mode: "strict": true in tsconfig.json
• Use Typed Routes for compile-time route safety (Next.js 15.5+)
• Avoid any type - use unknown for truly unknown types
• Use satisfies operator for type checking without widening
• Use Zod for runtime validation with z.infer<> for type inference

React 19 Patterns

• Default to Server Components, use 'use client' only when needed
• Use useActionState for form actions
• Use useOptimistic for optimistic UI updates
• Use use() for reading promises and context
• Enable React Compiler for automatic memoization

Next.js 15.5

• Use App Router with route groups for organization
• Fetch data in Server Components
• Use React.cache() for request memoization
• Implement streaming with Suspense boundaries

MoAI Integration

• Use Skill("moai-lang-typescript") for detailed patterns
• Follow TRUST 5 quality gates