TypeScript

TypeScript has become the default language for serious JavaScript projects. In 2026, the ecosystem has matured around a set of tools that make type-safe development fast and ergonomic — from Bun and Deno replacing Node.js to Biome replacing ESLint and Prettier.

Why TypeScript in 2026

• TypeScript 5.8 — using declarations, const type parameters, variadic tuple improvements
• Strict mode by default — modern projects start with "strict": true, no exceptions
• Runtime validation — Zod v4 and Valibot bridge the compile-time/runtime gap
• End-to-end type safety — tRPC, Prisma, and Drizzle ORM eliminate entire classes of bugs

Essential Toolchain

// package.json — modern TypeScript stack 2026
{
  "devDependencies": {
    "typescript": "^5.8.0",
    "tsx": "^4.x",          // Run TS directly, no compile step
    "vitest": "^3.x",       // Test runner
    "biome": "^2.x"         // Linter + formatter (replaces ESLint + Prettier)
  },
  "dependencies": {
    "zod": "^4.x",          // Runtime validation
    "hono": "^4.x"          // Ultrafast web framework
  }
}

# tsconfig.json — strict baseline
{
  "compilerOptions": {
    "strict": true,
    "target": "ES2022",
    "moduleResolution": "bundler",
    "verbatimModuleSyntax": true
  }
}

Learning Path

1. Strict mode fundamentals — unknown vs any, narrowing, discriminated unions
2. Advanced types — template literals, conditional types, infer, mapped types
3. Runtime validation — Zod schemas, parse vs safeParse, form validation
4. Type-safe APIs — tRPC for full-stack, OpenAPI codegen for external APIs
5. Performance tooling — Biome for linting/formatting, tsx for fast execution
6. Patterns — branded types, Result types, Builder pattern in TypeScript

Key Patterns