Master enterprise-grade TypeScript development with type-safe patterns, modern tooling, and framework integration. This skill provides comprehensive guidance for TypeScript 5.9+, covering type system fundamentals (generics, mapped types, conditional types, satisfies operator), enterprise patterns (e

Mastering Modern TypeScript Build enterprise grade, type safe applications with TypeScript 5.9+. Compatibility: TypeScript 5.9+, Node.js 22 LTS, Vite 7, NestJS 11, React 19 Quick Start When to Use This Skill Use when: Building type safe React, NestJS, or Node.js applications Migrating JavaScript codebases to TypeScript Implementing advanced type patterns (generics, mapped types, conditional types) Configuring modern TypeScript toolchains (Vite, pnpm, ESLint) Designing type safe API contracts with Zod validation Comparing TypeScript approaches with Java or Python Project Setup Checklist Before starting any TypeScript project: Type System Quick Reference Primitive Types Union and Intersection Types Type Guards The satisfies Operator (TS 5.0+) Validate type conformance while preserving inference: Generics Patterns Basic Generic Function Constrained Generics Generic API Response Wrapper Utility Types Reference Type Purpose Example Partial<T All properties optional Partial<User Required<T All properties required Required<Config Pick<T, K Select specific properties Pick<User, "id" \ "name" Omit<T, K Exclude specific properties Omit<User, "password" Record<K, V Object with typed keys/values Record<string, number ReturnType<F Extract function return type ReturnType<typeof fn Parameters<F Extract function parameters Parameters<typeof fn Awaited<T Unwrap Promise type Awaited<Promise<User Conditional Types Mapped Types Framework Integration React with TypeScript NestJS with TypeScript See [react integration.md](references/react integration.md) and [nestjs integration.md](references/nestjs integration.md) for detailed patterns. Validation with Zod Modern Toolchain (2025) Tool Version Purpose TypeScript 5.9+ Type checking and compilation Node.js 22 LTS Runtime environment Vite 7.x Build tool and dev server pnpm 9.x Package manager ESLint 9.x Linting with flat config Vitest 3.x Testing framework Prettier 3.x Code formatting ESLint Flat Config (ESLint 9+) Migration Strategies Incremental Migration 1. Add allowJs: true and checkJs: false to tsconfig.json 2. Rename files from .js to .ts one at a time 3. Add type annotations gradually 4. Enable stricter options incrementally JSDoc for Gradual Typing See [enterprise patterns.md](references/enterprise patterns.md) for comprehensive migration guides. Common Mistakes Mistake Problem Fix Using any liberally Defeats type safety Use unknown and narrow Ignoring strict mode Misses null/undefined bugs Enable all strict options Type assertions ( as ) Can hide type errors Use satisfies or guards Enum for simple unions Generates runtime code Use literal unions instead Not validating API data Runtime type mismatches Use Zod at boundaries Cross Language Comparison Feature TypeScript Java Python Type System Structural Nominal Gradual (duck typing) Nullability Explicit ( T \ null ) @Nullable annotations Optional via typing Generics Type level, erased Type level, erased Runtime via typing Interfaces Structural matching Must implement Protocol (3.8+) Enums Avoid (use unions) First class Enum class Reference Files [type system.md](references/type system.md) — Complete type system guide [generics.md](references/generics.md) — Advanced generics patterns [enterprise patterns.md](references/enterprise patterns.md) — Error handling, validation, architecture [react integration.md](references/react integration.md) — React + TypeScript patterns [nestjs integration.md](references/nestjs integration.md) — NestJS API development [toolchain.md](references/toolchain.md) — Modern build tools configuration Assets [tsconfig template.json](assets/tsconfig template.json) — Strict enterprise config [eslint template.js](assets/eslint template.js) — ESLint 9 flat config Scripts [validate setup.sh](scripts/validate setup.sh) — Verify TypeScript environment

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