What are some things that folks might not be aware of about TypeScript?

Ive been following Matt Pocock for a while and he started TypeScript tip tweets on Twitter a while ago. Ive found them super informative and its what prompted this post. Heres the latest one.

Matt Pocock

@mpocock1

TypeScript Tip #18

You can do some really, really neat stuff with assertion functions inside classes.

Here, we assert that the user is logged in and get proper inference on the user's logged in user id.

11:15 AM - 08 Apr 2022

So wonderful devs, what are some things that folks might not be aware of about TypeScript? If you can link to a TypeScript Playground example or an example in your favourite online editor, even better!