Internationalization (i18n)

Setup

```bash npm install i18n ```

```javascript const i18n = require('i18n');

i18n.configure({ locales: ['en', 'es', 'fr'], defaultLocale: 'en', directory: __dirname + '/locales' });

app.use(i18n.init); ```

Translation Files

```json // locales/en.json { "welcome": "Welcome", "greeting": "Hello, %s!" }

// locales/es.json { "welcome": "Bienvenido", "greeting": "¡Hola, %s!" } ```

Using Translations

```javascript app.get('/', (req, res) => { res.json({ welcome: req.__('welcome'), greeting: req.__('greeting', 'John') }); });

app.get('/lang/:locale', (req, res) => { res.cookie('language', req.params.locale); req.setLocale(req.params.locale); res.redirect('/'); }); ```

Key Takeaway

Store translations in JSON files. Detect language from headers or cookies. Format dates and numbers by locale.