type-fest VS ts-toolbelt

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.

There are a bunch of awesome type utility libraries that may boost your works on types, like ts-toolbelt, utility-types, SimplyTyped, etc., which you can already use.

We have only scratched the surface of type manipulation in Typescript, if you want to get your mind blown, checkout community projects like ts-toolbelt and type-challenges.

Do you mean https://github.com/millsp/ts-toolbelt? You didn’t provide a link so I’m not sure which repo you’re referring to.

I am guessing that since it does not exists as an built in type, in utility-types, or in ts-toolbelt that it currently isn't possible.

Since posting this, some comments have made me aware that ts-toolbelt has this feature and a couple other really useful ones built in. So their source code could be worth skimming through to see how they did things.

I was curios enough to dug the definition along with a related types Narrowable and Cast

ts-toolbelt has a "Path" Type https://github.com/millsp/ts-toolbelt