How do I declare a string that is of a specific length using typescript?

Question

For example a string that can only be two characters long, which could be used for an ISO country code.

I have used Google and looked through the documentation but cannot find the answer.

Answer 1

There isn't a way to specify a string length as a type.

If you have a finite list of country codes, you could write a string literal type:

type CountryCode = 'US' | 'CN' | 'CA' | ...(lots of others);

Answer 2

You can achieve this using a type constructor and a phantom type which are some interesting techniques to learn about. You can see my answer to a similar question here