TypeScript Tutorial

TypeScript (TS) is a superset of JavaScript: almost all valid JavaScript is valid TypeScript, plus static types. Code is compiled to JavaScript first, then run in the browser or Node.

Recommended path: finish the JavaScript tutorial first, then this track. TypeScript does not invent a new syntax — it adds types on top of JS. Skipping JS makes later lessons hard to follow. This tutorial targets TypeScript 5 and goes deeper than a cheat sheet: each lesson has explanations, comparison tables, pitfalls, practical snippets, and short exercises.

Types are erased after compile; at runtime you still have plain JavaScript. This site’s playground does not type-check — use VS Code or tsc to see errors.

Learning path

Start

1. What is TypeScript
2. Install and first file
3. Basic types
4. Functions

The type system

5. Objects: interface and type
6. Unions and narrowing
7. Arrays and tuples
8. keyof and indexed access types
9. Mapped types
10. Generics
11. Utility types
12. Conditional types and infer
13. Type guards and assertions
14. Enums and as const

Async and projects

15. Async and Promise
16. Classes
17. Modules
18. DOM and event types
19. Declaration files and @types
20. tsconfig
21. Summary

Next: What is TypeScript