Seven days per course · Your own pace
Build on JavaScript with types that describe your data and catch mismatched assumptions. Learn to read compiler errors, model alternatives and validate the values your program receives.
Enable JavaScript to edit and type-check this example.
Try a wrong type, read the diagnostic, then fix it and choose Check & run.
Find your starting point
New to TypeScript, rather than new to programming. Know JavaScript variables, functions, arrays and objects first. Every available course is public, with no sign-in required.
After JavaScript beginner
Read compiler errors and describe functions, objects and alternatives without losing sight of runtime behavior.
TypeScript beginner + JavaScript async basics
Preserve useful relationships across reusable functions, decoders and asynchronous boundaries.
After intermediate TypeScript
Design library APIs whose types preserve important relationships, then test the declarations consumers receive.
Still learning JavaScript? Build the basics in JavaScript beginner first.
More than a page to read
You learn a rule by using it. Each day gives you chances to predict, experiment and solve a problem with less help.
Read a short explanation, predict the output and run the example. Change an input to find out whether you understood the rule.
Try each exercise first. Open an idea hint, then a first-step hint if you need it. Compare your approach with the worked solution afterward.
Use checkpoints to work independently. Finish a project, tackle a different brief and return a few days later to practise from memory.
Beginner, day by day
Plan around 60–90 minutes of active study per day. Split a day into smaller sessions when needed; the order matters more than the calendar. Delayed review is extra.
Separate type checking from execution and diagnose simple mistakes.
Describe reusable function contracts and records with optional data.
Model alternatives and handle absent values with real evidence.
Handle missing lookups and summarize collections without mutation.
Preserve useful type relationships without losing domain information.
Turn unknown JSON into trusted records with explicit failure results.
Migrate, test and extend a familiar JavaScript core, then solve a fresh brief.
Something to show for your work
By the end of beginner, the pieces come together in a typed study-planner core. You will know where the data lives, how it changes and how to check the result.
Describe the planner’s data with types, validate outside input and test the behavior. Then transfer the same habits to a fresh problem.
Explore the final dayYour first experiment
Planned: 50 minutesThe small example at the top already uses the same idea: store a few sessions and derive a useful total. The course teaches each piece before asking you to build the complete planner.
The real TypeScript compiler checks this example before it runs. Types help catch mistakes; they do not replace runtime validation or tests.
Before you begin
Start with the right expectations, then spend your time making things work.
Learn JavaScript basics first. These lessons assume you can write a function, traverse an array and read an object. TypeScript beginner focuses on adding types to those skills.Start with JavaScript beginner →
Yes. Check types uses the TypeScript compiler with strict checks. Diagnostics include the message and source location; Check & run executes only after checking succeeds.
No. Types describe constraints the compiler can check. External data still needs validation, and the behavior your application promises still needs tests.
All three TypeScript levels are public. No sign-in or local installation is needed for the core lessons. Downloadable projects provide a bridge to local work.
Start with one small program
No setup checklist. Open Day 1, change a line and see what happens. The rest can follow one lesson at a time.