Value validation

[threema-danilo]

Is it possible to do validations on the value, which is not part of the type information (e.g. only allowing numbers 0-255, or only strings matching a RegEx)? Or is that out of scope?

There seems to be code to validate the length of arrays, but I think right now this is only used for tuples, which are covered by TypeScript's type system.

[marvinhagemeister]

Yes, that's what the .assert() method is for. It allows you to add a custom validator function and pass a custom error message. In your case it would look like this:

import * as v from "@badrap/valita";

const schema = v
  .number()
  .assert((v) => v >= 0 && v <= 255, "Must be in between 0 or 255");

schema.parse(2); // works
schema.parse(-1); // Throws "Must be in between 0 or 255"
schema.parse(300); // Throws "Must be in between 0 or 255"

For regex you can do the same:

import * as v from "@badrap/valita";

const schema = v
  .string()
  .assert((v) => /my-cool-regex/.test(v), "Must match regex");

Although to be fair a buit-in regex matcher would be even nicer. Sounds like a feature that's easy enough to add via a PR 👍

[threema-danilo]

Ah, nice, thanks for the quick reply! Might be something worth mentioning in the README 🙂

[threema-danilo]

Thank you!