typescript-development

name	typescript-development
description	Covers TypeScript 5+, React 18+, Next.js 14+ App Router, Zustand, Tailwind CSS, and Vitest testing. Use when writing TypeScript applications, React components, or Node.js services. Not for UI/UX design (use interface-design), database schema (use database-design), or Python (use python-development).

TypeScript Development

Modern TypeScript development with React ecosystem.

Contents

• Critical Rules
• Verification
• Quick Reference
• Topics

Critical Rules

Always

• Use strict mode in tsconfig
• Type all function parameters and returns
• Handle null/undefined explicitly
• Use Server Components by default
• Validate on both client and server
• Test with screen readers
• Measure before optimizing

Never

• Use any (use unknown with type guards)
• Use ! (non-null assertion) without justification
• Store server data in client state (use React Query)
• Rely on color alone for information
• Create new functions in render
• Skip error handling for API calls

Verification

After Editing TypeScript/JavaScript Files

Type Checking:

• If tsc is available, run: npx tsc --noEmit
• Checks entire project against tsconfig.json
• Common fixes: add proper type annotations, use union types for nullable values, import types from @types/* packages

Linting:

• If eslint is available, run: npx eslint {files}
• To auto-fix issues: npx eslint --fix {files}

Bundle Analysis (for component files):

• Check file size and LOC when modifying components
• Warn if file > 100 KB or > 500 lines of code
• Consider breaking into smaller components for large files
• Use code splitting and lazy loading for heavy dependencies

Before Committing

• Run type checker on the entire project
• Run ESLint on modified files
• Verify component sizes are reasonable
• Check for console errors and warnings

Quick Reference

Layer	Default	Alternatives
Language	TypeScript 5+	JavaScript (ESM)
Runtime	Node.js 22+	Bun, Deno
Framework	Next.js 14+	Vite, Remix
UI Library	React 18+	-
State (Client)	Zustand	Context + Reducer
State (Server)	React Query	SWR
Forms	React Hook Form + Zod	-
Styling	Tailwind CSS + CVA	CSS Modules
Testing	Vitest + RTL	Jest
E2E Testing	Playwright	Cypress
Package Manager	pnpm	npm, yarn

Topics

Topic	Use For
Core	Project setup, tsconfig, modern TS features, type utilities
React	Components, hooks, Context API, performance patterns
Next.js	App Router, Server/Client Components, Server Actions, routing
Types	Advanced types, generics, conditional types, type guards
State	Zustand, React Query, Context + Reducer, URL state
Forms	React Hook Form, Zod validation, Server Actions integration
API	Fetch wrappers, React Query, tRPC, GraphQL, WebSockets
Testing	Vitest, React Testing Library, MSW, Playwright E2E
Styling	Tailwind CSS, CVA variants, dark mode, responsive design
Performance	Bundle analysis, code splitting, memoization, Web Vitals
Accessibility	WCAG compliance, ARIA, keyboard navigation, screen readers
Mobile	React Native, Expo, navigation, platform-specific code
ESM	ESM patterns, JSDoc types, JS vs TS decision guide