TypeScript in a Month 🚀

Learn core TypeScript in ~4 weeks the way you actually get good at it: by writing code. 20 hands-on, test-driven blocks under strict mode, each with runnable examples and verified reference solutions.

A complete, free course for JavaScript developers learning TypeScript. You don't read about types — you implement functions, make failing tests pass, and satisfy the compiler under strict. Perfect for self-study, a study group, or a workshop syllabus.

Why this course

• 🧪 Test-driven — every block ships failing tests; you make them green. No passive reading.
• 🔒 Strict from day one — strict, noUncheckedIndexedAccess, noUnusedParameters, and more, so you learn the habits real codebases expect.
• ✅ Verified solutions — every reference answer is itself tested (npm run test:solutions), so what you compare against is guaranteed correct.
• 🧠 Type-level tests — exercises about types are checked with expectTypeOf, not just runtime asserts.
• 📦 Real-world finish — modules, async, the Result<T, E> pattern, declaration files, and a multi-module capstone library.

Use this template

This is a GitHub template repository — click Use this template to get your own copy you can commit solutions to and track progress with git. (Or just fork it.)

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Quick start

# 1. Create your copy (Use this template) or clone
git clone https://github.com/Rossoline/typescript-learn.git
cd typescript-learn

# 2. Install dependencies (Node.js 18+)
npm install

# 3. Run all tests — most fail until you solve the exercises
npm test

# 4. Work one block at a time, re-running on save
npx vitest blocks/01-getting-started

Recommended workflow per block

1. Read the block's README.md.
2. Open src/examples.ts, read it, and run it to see the output:

   npx tsx blocks/01-getting-started/src/examples.ts

3. Open src/exercises.ts and implement each // TODO.
4. Run that block's tests until they all pass:

   npx vitest blocks/01-getting-started

5. Check your types are clean, then compare with solutions/:

   npm run typecheck

Type-only blocks (14 & 18): there the exercise is to write types (mapped/ conditional types, a .d.ts), so the type checker is the test — run npm run typecheck and make the errors in that block disappear.

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What's in each block

blocks/NN-topic/
├── README.md          # the topic explained, with examples and the exercise list
├── src/examples.ts    # runnable, worked examples
├── src/exercises.ts   # practice tasks with // TODO stubs — your job
├── tests/             # automated tests (Vitest) — make them pass
└── solutions/         # reference solutions (try the exercises first!)

Curriculum at a glance

The full day-by-day plan is in PLAN.md. Twenty blocks across four weeks:

Week	Theme	Blocks
1	Foundations	01 Getting Started · 02 Basic Types · 03 Functions · 04 Objects & Type Aliases · 05 Union & Literal Types
2	Shaping Types	06 Interfaces · 07 Classes · 08 Enums · 09 Narrowing · 10 Type Assertions
3	Advanced Core	11 Generics · 12 Utility Types · 13 keyof / typeof / Indexed Access · 14 Mapped & Conditional Types · 15 Modules
4	Practical TS	16 Async & Promises · 17 Error Handling & Result Types · 18 Declaration Files & @types · 19 tsconfig & strict mode · 20 Capstone Project

Scripts

Command	What it does
npm test	Run every block's tests (your progress).
npm run typecheck	Type-check the whole project (tsc --noEmit).
npm run test:solutions	Verify the reference solutions all pass.
npx vitest blocks/NN-...	Run/watch a single block.
npx tsx <file>	Run any .ts file directly.

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Editor setup

Works out of the box in VS Code (install the Vitest extension for inline test running) and WebStorm / IntelliJ (right-click a *.test.ts → Run 'Vitest'; enable Toggle auto-test to re-run on save). TypeScript errors show inline as you type in both.

How testing works

Each exercise file exports functions or values; the matching test imports them and asserts behavior. Implement a // TODO correctly and its test goes green. The goal isn't only passing tests — it's writing code the compiler accepts under strict.

Self-study tips

• Use this template (or fork) so you can commit your solutions and build a streak.
• Commit after each block (git commit -m "block 03 done").
• Don't skip the READMEs — the exercises assume you read them.
• Stuck for ~15 min? Read the solution, understand it, then re-implement from memory.

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If this helped you learn TypeScript, please ⭐ the repo — it helps others find it. Contributions and issue reports are welcome. Happy typing! 🧠