Fallback Chains

When a message is not found in the current locale, Fluenti tries:

1. Current locale
2. Fallback chain (if configured)
3. fallbackLocale (if set)
4. Returns the message ID

Configuration

const i18n = createFluentVue({
  locale: 'zh-TW',
  fallbackLocale: 'en',
  messages: { en, 'zh-CN': zhCN, 'zh-TW': zhTW },
  fallbackChain: {
    'zh-TW': ['zh-CN', 'en'],
    'pt-BR': ['pt', 'en'],
    '*': ['en'],
  },
})

With this config, when locale is zh-TW:

1. Try zh-TW catalog
2. Try zh-CN catalog (from fallbackChain)
3. Try en catalog (from fallbackChain)
4. Try en catalog (from fallbackLocale)

Regional Variants

Instead of duplicating an entire catalog for en-GB, let it fall back to en and only translate the differences:

createFluent({
  locale: 'en-GB',
  fallbackLocale: 'en',
  fallbackChain: {
    'en-GB': ['en'],
    'zh-TW': ['zh-CN'],
    'pt-BR': ['pt'],
  },
  messages,
})

Missing Handler

For custom behavior when a message is not found:

const i18n = createFluentVue({
  locale: 'en',
  messages,
  missing: (locale, id) => {
    console.warn(`Missing translation: ${locale}/${id}`)
    return undefined // or return a fallback string
  },
})