typescript-json-schema VS io-ts

Typescript to JSON Schema

For anyone using both TypeScript and JSON schemas, but wanting to use TypeScript as the source of truth, I highly recommend the following library: [ts-json-schema-generator](https://github.com/YousefED/typescript-json-schema).

It does exactly what it says in the box: turns your TypeScript `types` / `interface` into machine-readable JSON schemas.

The library has a few open issues (does not deal well with some edge cases of composing Omit<> on sum types, and does not support dynamic (const) keys), but compared to manually writing JSON schemas, it's been amazing!

There are a bunch of tools to generate JSON-schema from a TS codebase, ie https://github.com/YousefED/typescript-json-schema

Now that cool thing we wanted to do? This library does exactly that!

> For more complex cases I find myself wishing I could just turn Typescript into some kind of schema validation for JSON.

Not sure if this is what you're looking for, and whether it's powerful and expressive enough for your use case, but you can use typescript-json-schema¹ for this, and validate with eg ajv.

¹https://github.com/YousefED/typescript-json-schema

Use https://github.com/YousefED/typescript-json-schema to go from TS -> json schema

For what it's worth, thanks to TypeScript transformers (a feature baked into the compiler), one can create a transformer library that verifies an object is valid for any TypeScript type and conveys that information to the typechecker. And indeed, it's already been made. It allows to parse unknown into a given T. This is nice, because one can generate a JSON schema out of a TS type, for other languages/codebases to integrate safely.

This is why I originally started a project to convert ts to json schema; https://github.com/YousefED/typescript-json-schema (and also check out a good alternative https://github.com/vega/ts-json-schema-generator)

Typescript JSON schema

Qué rico. Si tenés chance meté un proceso de code review fuerte, y para el tema de I/O probá a usar https://github.com/Effect-TS/schema ó https://github.com/gcanti/io-ts que les da una solución obvia al tema de "tipos para lo que devuelva el backend", aunque es en realidad mucho más capaz que eso.

My fave is still io-ts (https://github.com/gcanti/io-ts/blob/master/docs/index.md) as I find it more flexible than zod at the ingress. The author is also working on the Effect ecosystem which also looks interesting.

I’ve been using io-ts for this and been very happy with it. [1] It’s similar to Swift’s Coding protocol in case you’re familiar.

[1] https://gcanti.github.io/io-ts/

Yeah, there are a few new concepts and it's not the easiest to pick up right away. The best introduction is here on the main documentation page.

We use https://github.com/gcanti/io-ts/blob/master/Decoder.md which has a very similar interface. It can even be used to mutate the data using https://github.com/gcanti/io-ts/blob/master/Decoder.md#the-parse-combinator.

A good way to significantly improve the reliability of your app is via improving type-safety by moving away from using any to unknown. One relevant example could be when you type your backend responses and when stringifying JSON to using unknown combined with some sort of runtime type checking. It can be done either by using built-in functionality like type guards or using an external library like io-ts, zod or yup.

Usage of TypeBox is similar with io-ts and zod, but it is much powerful and faster than them. Also, TypeBox can generate JSON schema very easily. Therefore, if you're looking for a validator library for new project and not suffering from legacy codes, I think TypeBox would be much better choice than io-ts and zod. TypeBox can totally replace them.

This check can be done with different libraries like: io-ts, typebox, or zod. These libraries allow you to create objects that represent your typescript definitions. Then, these objects can be used at runtime to validate the received data, in addition, you can also convert this object to a Typescript definition to have all the benefits of using typescript. These objects can be called schema validations because they are responsible for the data validation.