File-Based Locale

Create a locale/ folder beside bro.config.js. Each file exports a translation object, and its filename becomes the locale:

locale/
├── en.js
├── fr.js
└── ar.js

locale/en.js:

export default {
  welcome: 'Welcome, {name}!'
};

locale/fr.js:

export default {
  welcome: 'Bienvenue, {name} !'
};

The same structure also works with names such as en-US.js, English.js, or Arabic.js.

Configure the Default Locale

import { defineConfig } from 'bro-framework';
 
export default defineConfig({
  locale: {
    defaultLocale: 'en'
  }
});

The locale/ directory and en default are automatic. The configuration is only needed when you want a different fallback locale or directory.

Use Translations in Routes

bro.js selects the locale from the request's Accept-Language header and injects the t function into every route context:

import { defineRoute } from 'bro-framework';
 
export default defineRoute({
  handler: async ({ t }) => ({
    message: t('welcome', { name: 'Sam' })
  })
});

Advanced Header Negotiation

The locale engine natively implements RFC 9110 quality values for HTTP content negotiation.

• It parses headers like Accept-Language: fr-CH, fr;q=0.9, en;q=0.8, de;q=0.7, *;q=0.5.
• Locales explicitly marked with q=0 are strictly rejected.
• Valid requests are sorted in descending order of quality.
• For each requested locale, it attempts an exact match (e.g. fr-CH). If missing, it automatically attempts a language-only fallback (e.g. fr).
• If the entire list is exhausted with zero matches, it falls back to your configured defaultLocale.
• If a specific translation key is missing from a locale file, it falls back to the default locale file. If missing everywhere, the key string itself is returned.

Nested Keys

Translation objects can be organized by feature:

export default {
  auth: {
    loggedIn: 'You are authenticated.'
  }
};

Use the dotted key in a route:

const message = t('auth.loggedIn');

The generated SDK also supports the locale header:

import { setLocale } from './bro-sdk.js';
 
setLocale('fr');