Module 1

The lessons.

Eleven lessons on the type system. Every exercise runs against the real TypeScript compiler in your browser. Free, no signup.

01	Your TypeScript reads like Python	the thesis
02	Stop annotating everything	inference is the default
03	Duck typing, formalized	structural typing
04	Unions instead of inheritance	the isinstance habit
05	None, null, undefined: three nothings	Optional[str] becomes string \| undefined
06	Discriminated unions	the workhorse pattern
07	Classes everywhere: the Python tell	when a class is still right
08	unknown vs any	any is worse than untyped Python
09	Generics without fear	TypeVar maps to T
10	The pydantic-shaped hole	zod at the boundary
11	async/await: same keywords, different machine	promises are eager