type-fest VS runtypes

Related: https://github.com/sindresorhus/type-fest/blob/main/source/o...

Typescript doesn’t natively provide an Opaque type that we can use to define a string that has already been localized. If the data looks like a string, Typescript will consider it a string. We can however use utility types that simulate opaque types, like the Opaque definition in type-fest:

With these powerful features, you can create dynamic and expressive types. One last thing I want to mention before moving on, is that you can install libraries with which you can add more types to your project like type-fest or utility-types. These libraries contain a lot of useful types that you can use in your project.

Also, it’s not as restrictive as mutability tools — if you know what you are doing and want to ignore this limitation for a particular case, you can apply the -readonly modifier or the Writeable type from type-fest or ts-essentials.

Remember you can derive one type from another type so you can make sure they don't diverge. SetOptional type util

Some folks have built whole SQL databases and DSL compilers in the TS type system. These tend to be toy projects with disclaimers not to use them. But the type system being Turing complete[0] (for better or worse), pretty much whatever you can imagine. This project[1] is one I actually return to frequently for practical ideas.

0: https://github.com/microsoft/TypeScript/issues/14833

1: https://github.com/sindresorhus/type-fest

Have a look at SetRequired and SetOptional in type-fest

Try the Exact method provided by Type Fest, looks like it does what you're looking for

This is a fairly common scenario and available via libraries like type-fest or implementable with a couple lines of code.

In terms of which runtime checker I should use. The first tutorial I saw suggested 'Zod', doing a bit more searchign yielded other options such as 'runtypes'.

Runtypes would probably be a better example.

this has been solved by several packages, runtypes https://github.com/pelotom/runtypes being my favorite

I personally like https://github.com/pelotom/runtypes because it bundles your Schema Info and the corresponding Typescript types

When I have to deal with data from API calls, I usually use a runtime typing library like Runtypes or Zod to check the responses at the boundary. These libraries can automatically give you TS types (using their static or infer utilities) to use throughout the rest of the project.

Also runtypes and (as mentioned below) zod.

Seconding the recommendation to use a library for this. runtypes and io-ts are two other alternatives.

I wouldn't reinvent the wheel: https://github.com/pelotom/runtypes

What does your library provide that others don't? For example: https://github.com/colinhacks/zodhttps://github.com/hapijs/joihttps://github.com/jquense/yuphttps://github.com/gcanti/io-tshttps://github.com/pelotom/runtypeshttps://github.com/sindresorhus/ow