Common - Validators

Reusable input validators - currently just email. More to come.

FF_Validators (English defaults)

Drop-in for ad-hoc use:

import { FF_Validators } from 'firstly'

// In a Remult entity:
@Fields.string({ validate: FF_Validators.email })
email = ''

// Or as a pure check, e.g. in a UI for live inline feedback:
const verdict = FF_Validators.checkEmail(typed)
if (verdict !== true) showError(verdict)

What email accepts:

• the empty string is valid (so a default-empty optional field doesn’t fail)
• otherwise, RFC-ish syntax check via regex
• rejects placeholder / test domains: @example.com, *.test, *.invalid, localhost, etc.

createValidators(messages?) for localized messages

The default FF_Validators returns English messages. For a project that speaks something else - or, more interestingly, for an app that needs to return a message in the current user’s locale at validation time - build your own validators with createValidators:

src/lib/App_Validators.ts

import { createValidators } from 'firstly'

export const App_Validators = createValidators({
  email: {
    invalid: 'Email invalide',
    invalidDomain: 'Domaine invalide',
    blockedDomain: 'Email de test/exemple non accepté',
    blockedTld: 'TLD de test/exemple non accepté',
  },
})

Per-request locale (i18n)

Each message can be a literal string OR a function returning a string. The function form is called at validation time, so it picks up the current request’s locale every time the validator fires - perfect for paraglide, i18next, lingui, etc.

import { createValidators } from 'firstly'

import * as m from '$lib/paraglide/messages'

export const App_Validators = createValidators({
  email: {
    invalid: () => m.email_invalid(),
    invalidDomain: () => m.email_invalid_domain(),
    blockedDomain: () => m.email_blocked_domain(),
    blockedTld: () => m.email_blocked_tld(),
  },
})

A user with lang: 'fr' calling the same validator gets the French message; a user with lang: 'en' gets the English one - because each call to m.email_invalid() resolves the locale from your i18n lib’s current context (cookies, AsyncLocalStorage, etc.).

Note

checkEmail(value) returns true when valid, or the message string when invalid. email is the same logic wrapped as a Remult Validator so it plugs into @Fields.string({ validate: ... }). Same source of truth, two shapes for two consumers.