Learn TypeScript | Code & Run

TS tutorial & compiler: generics, type puzzles and interview questions

Learn TypeScript step by step, from your first type annotation to generics and conditional types. This TypeScript tutorial pairs 101 short courses with a code editor that checks your types as you type, daily puzzles and interview practice, so you write typed code instead of only reading about it.

WHAT YOU'LL LEARN
352 lessons in 101 courses, levelled A1 to C2:
• Basics: why types matter, basic types, arrays, tuples and enums, functions and annotations, literal types, unknown, never and void
• The type system: interfaces and aliases, union and intersection types, narrowing and guards, discriminated unions, the satisfies operator
• Generics: generic functions and types, constraints, conditional types, mapped and template literal types, the infer keyword, custom utility types
• Real projects: React, Node.js and Express, type-safe API clients, runtime validation with Zod, testing with Jest, tRPC, GraphQL, Next.js
• Tooling: strict mode and tsconfig, modules and declaration files, build tools and bundlers, monorepos, migrating a JavaScript project
The first course is free. Lessons mix short explanations with questions and small code tasks.

TYPESCRIPT LAB: THE REAL COMPILER ON YOUR PHONE
The compiler runs on the device, so your code is checked instantly.
• Type Gym: 24 puzzles and a puzzle of the day
• Debug Arena: fix broken code before the clock runs out
• Weekly duel: one puzzle for everyone each week, ranked on a leaderboard
• Project tracks: build a typed API client, type-safe forms and a state machine, with every step checked by the compiler and by tests
• Interview simulator: 30 questions in a timed set, with a graded report
• Weakness radar: see which topics you still get wrong

TYPESCRIPT EDITOR WITH LIVE TYPE CHECKING
• Write code in the built-in editor and see type errors underlined as you type
• Type Explorer shows the type at your cursor, including union members
• Run your code and see the output
• AI Tools in the editor review your program and suggest a fix you can apply
• Save your programs and open them again later

20 GUIDED PROJECTS AND 60 CODING MISSIONS
Build small programs one step at a time, each step checked when you run it. Then practise with 60 short coding missions in three levels, from Hello World to algorithms. The first project and the first two missions are free.

AI MENTOR
Confused by a generic constraint or a compiler error? Ask the AI Mentor and get an explanation in plain language. Free users get a few AI questions every day; Pro removes the daily limit.

MORE WAYS TO PRACTISE
• Quizzes with 50 questions and a TypeScript cheat sheet
• 50 interview questions with answers
• World Coding Challenge: three global rounds every day; solve them in TypeScript or another language
• Streaks, XP and daily reminders at the time you choose
• The app is available in 22 languages

WHO IT'S FOR
• JavaScript developers moving to TypeScript
• React and Node.js developers who want typed code end to end
• Beginners who want to learn programming the typed way from the start
• Developers preparing for a coding interview

FREE AND PRO
Free: the first course, the first guided project and project track, two coding missions, daily Lab practice and a daily AI Mentor allowance. The free version shows ads.
Pro: every course, project, track and mission, unlimited AI Mentor and Lab practice, the full error list in the editor, the certificate exam and no ads.

TypeScript is a trademark of Microsoft Corporation. This app is not affiliated with or endorsed by Microsoft.

Download Learn TypeScript | Code & Run and write your first typed program today.