typescript-development

Hands-on TypeScript 5.x engineer. Designs system architecture and implements production-ready code using modern tooling (pnpm/bun, Vite/tsup, Vitest, ESLint 9 flat config, Zod/Valibot). Type-safe, strict-mode, well-tested. TRIGGER WHEN: planning a new TypeScript project, designing architecture, making tech-stack decisions, implementing TS features, migrating JavaScript to TypeScript, or setting up a monorepo. DO NOT TRIGGER WHEN: the task is React-specific performance optimization (use react-development:react-performance-optimizer) or Node.js simple bug fixes.

Knip finds unused files, dependencies, exports, and types in JavaScript/TypeScript projects. Plugin system for frameworks (React, Next.js, Vite), test runners (Vitest, Jest), and build tools. TRIGGER WHEN: cleaning up TypeScript/JavaScript codebases, optimizing bundle size, or enforcing strict dependency hygiene in CI. DO NOT TRIGGER WHEN: the target is a Python codebase (use python-dead-code with vulture/ruff instead).

Enterprise-grade TypeScript depth covering the advanced type system (generics, mapped/conditional types, satisfies operator, branded types, discriminated unions, template literal types), JS-to-TS migration playbooks, modern toolchain setup (tsconfig strict, Vite 7, Vitest, ESLint 9 flat config, pnpm), validation patterns with Zod, type-safe React integration, NestJS API design, and LangChain.js typing. TRIGGER WHEN: migrating a JavaScript codebase to TypeScript, bootstrapping a new TS project (tsconfig + ESLint + Vite/Vitest), writing or refactoring code that uses advanced type patterns (generics, mapped/conditional types, satisfies, branded types), designing Zod schemas for runtime validation, building type-safe NestJS APIs, doing deep React + TypeScript work (typed hooks, generic components, discriminated props), or typing LangChain.js applications. Also trigger when comparing TypeScript with Java/Python enterprise approaches. DO NOT TRIGGER WHEN: writing routine TS/JS without advanced type work (use typescript-development:typescript-write), reviewing React performance specifically (use react-development:review-react), tuning Node.js bundling/packaging unrelated to TS, or doing dead-code detection alone (use typescript-development:knip).

Write TypeScript and JavaScript code following modern best practices and coding standards. TRIGGER WHEN: writing or reviewing TypeScript/JavaScript code, including types, generics, async patterns, module boundaries, and style conventions. DO NOT TRIGGER WHEN: the task is framework-specific React performance (use react-development), Node.js build/packaging, or enterprise-grade deep-dive (use mastering-typescript skill).