TypeScript at application boundaries
Validate unknown data, model state transitions and preserve type relationships.
Prerequisite: TypeScript foundations · 80 minutes of guided study
3 focused lessons; use tsc --strict for full type checking.
Start first lesson →What you’ll be able to do
- Preserve the relationship between records and keys.
How to study this course
Follow the numbered modules. Read the example, explain why it works, attempt the exercise, then compare your result with the supplied checks.
Setup: A modern browser. JavaScript, TypeScript, Python and SQLite exercises run here; project workshops state their additional setup.
Times estimate guided reading and practice. Projects and revision can take longer.
Course syllabus · 3 lessons
Engineering practice
- Validate untrusted JSON at the boundary25 min · Browser exercise →
unknown requires evidence; a type assertion supplies none.
- Model legal state transitions30 min · Browser exercise →
A reducer makes transition rules reviewable and testable.
- Keep generic grouping type safe25 min · Browser exercise →
Preserve the relationship between records and keys.