formgator

A validation library for JavaScript FormData and URLSearchParams objects.

Basic Usage

If you have a form with the following fields:

<form method="post">
  <label>
    User Name:
    <input type="text" name="username" required />
  </label>
  <label>
    Birthday:
    <input type="date" name="birthday" />
  </label>
  <label>
    <input type="checkbox" name="newsletter" />
    Subscribe to newsletter
  </label>
  <button type="submit">Submit</button>
</form>

You can use formgator to validate the form data:

import * as fg from "formgator";

// Define a form schema
const schema = fg.form({
  username: fg.text({ required: true }),
  birthday: fg.date().asDate(),
  newsletter: fg.checkbox(),
});

async function handle(request: Request) {
  // Retrieve the form data from the request
  const form = await request.formData();

  // Validate the form data
  const data = schema.parse(form);

  // data is now an object with the following shape:
  // {
  //   username: string,
  //   birthday: Date | null,
  //   newsletter: boolean,
  // }

  // If the form data is invalid, an error will be thrown
}

API

You can expect formgator to expose a validator for all possible <input type="..."> values.

Usage with SvelteKit

formgator exposes a SvelteKit adapter that can be used to validate form data in SvelteKit form actions.

// +page.server.ts
import * as fg from "formgator";
import { formgate } from "formgator/sveltekit";

export const actions = {
  login: formgate(
    {
      email: fg.email({ required: true }),
      password: fg.password({ required: true }),
    },
    ({ data }) => {
      // data.email and data.password are guaranteed to be strings
      // The form will be rejected as 400 Bad Request if they are missing or empty
    },
  ),
};

Disclaimer

This package is still in development and the API is subject to change. API will be stabilized in version 1.0.0.

License

This package is licensed under the MIT license.

This license only applies to the formgator package and not the rest of the code in this repository.