[atwood22]

Have you seen the library runtypes for TS? It lets you specify types using a library rather than pure TS type syntax. The library code looks very similar to the normal TS type syntax, but when you use the type you get input validation for free. And of course the type TS thinks the type is matches what you’d expect based on your type definition.

Also, TS let’s you specify things like ”this type is an array of 4 numbers”. Obviously TS isn’t perfect, but it’s pretty good!

[thinkingkong]

It lets you specify the type of length of an array but it has absolutely no protection other than initialization. For example, you can _easily_ push to an `Array<number>(5)` so... other than initializing by hand with all positional arguments you aren't getting any safety.

[atwood22]

That’s an interesting idea. You could define a custom type that has the type of [number, number] and combine it with Omit to remove methods that allow extending the array.