[christofosho]

This is not exactly a codebase, but I believe it merits mention in this thread as a great TypeScript learning resource.

https://type-level-typescript.com/

A short online course about intermediate-to-advanced level TypeScript.

[satvikpendem]

See also, Total TypeScript: https://github.com/total-typescript

The course is paid but the exercises are free on GitHub, you just won't get any explanations if you get an exercise wrong.

[tejinderss]

Similarly the typescript courses at http://executeprogram.com are pretty good.