STAGE 01 LESSONS 01–07
Foundations
Learn the JavaScript you need and write your first strict TypeScript program.
Start stageFREE COURSE / TYPESCRIPT 7
Learn TypeScript.
Build apps
and libraries.
Learn how JavaScript runs and how TypeScript checks your code. Then build, test, and package software you can maintain.
Free to read. No account needed.
type Job =
| { state: "queued"; id: string }
| { state: "done"; result: string };
function describe(job: Job) {
if (job.state === "done") {
return job.result; // narrowed to string
}
return `Waiting: ${job.id}`;
}
THE LEARNING LOOP
Predict the type.
Check the code.
Run the JavaScript.
36LESSONS WITH EXERCISES
05STAGES
72CODE EXAMPLES & DRILLS
01PRODUCTION CAPSTONE
YOUR LEARNING PATH
Start with the basics.
Build at every stage.
Write your first program, learn the type system, then build applications and libraries. Each stage ends with a project.
STAGE 02 LESSONS 08–17
The type system
Use inference, narrowing, and generics to describe your data.
Start stageSTAGE 03 LESSONS 18–25
Real applications
Work with APIs, async resources, runtime validation, and tests.
Start stageSTAGE 04 LESSONS 26–31
Libraries & scale
Design public APIs, publish packages, and manage a growing codebase.
Start stageSTAGE 05 LESSONS 32–36
Advanced & production
Choose types and tools that keep your software easy to change.
Start stageTYPES AND RUNTIME
Types check your code.
Validation checks your data.
EXTERNAL DATAUNKNOWNPARSE + VALIDATETRUSTED TYPE
Let TypeScript infer what it can. Use unions to describe valid states, and validate external data before you trust it.
Learn runtime validationTHE FINAL PROJECT
Build a job
execution platform.
A CLI, HTTP API, async executor, persistence, cancellation, and a reusable package. Build it in stages and test each part.
View the project- 01 / Model the domain
- 02 / Validate the boundaries
- 03 / Manage async execution
- 04 / Package & test
- 05 / Ship & maintain