dupipcom/the-i18n

Task: Audit and maintain internationalization across all 33 supported locales.

Role: You're an internationalization specialist ensuring the app works correctly in all languages.

Supported Locales

ar, be, bg, cs, de, el, en, es, et, fi, fr, he, hi, hr, hu, id,
it, ja, ko, lt, lv, nl, no, pl, pt, ro, ru, sk, sl, sv, th, tr, uk, zh

Default locale: en

i18n Architecture

• Translation files: src/locales/{locale}.json
• Context: useI18n() hook provides t() function
• Date formatting: formatDate() with locale support
• Task localization: localeKey field for translation lookup

Audit Steps

1. Find Missing Translations

# Extract all translation keys used in code
grep -rh "t\(['\"]" --include="*.tsx" --include="*.ts" src/ |
  grep -oP "t\(['\"][^'\"]+['\"]" |
  sort -u > used_keys.txt

# Compare with en.json

2. Find Hardcoded Strings

# Find potential hardcoded text in components
grep -r ">[A-Z][a-z].*<" --include="*.tsx" src/components/
grep -r "title=\"[A-Z]" --include="*.tsx" src/
grep -r "label=\"[A-Z]" --include="*.tsx" src/

3. Verify All Locales Have Same Keys

// Compare key counts across locale files
import en from '@/locales/en.json'
import es from '@/locales/es.json'

const enKeys = Object.keys(flattenObject(en))
const esKeys = Object.keys(flattenObject(es))
const missing = enKeys.filter(k => !esKeys.includes(k))

Translation File Structure

{
  "common": {
    "save": "Save",
    "cancel": "Cancel",
    "delete": "Delete",
    "loading": "Loading..."
  },
  "auth": {
    "login": "Log in",
    "logout": "Log out",
    "signUp": "Sign up"
  },
  "tasks": {
    "title": "Tasks",
    "addTask": "Add task",
    "complete": "Mark complete"
  },
  "errors": {
    "generic": "Something went wrong",
    "notFound": "Not found",
    "unauthorized": "Please log in"
  }
}

Usage Patterns

Basic Translation

import { useI18n } from '@/lib/i18n'

function Component() {
  const { t } = useI18n()
  return <h1>{t('page.title')}</h1>
}

With Interpolation

// en.json: { "greeting": "Hello, {name}!" }
t('greeting', { name: user.name })

Pluralization

// en.json: { "items": "{count, plural, one {# item} other {# items}}" }
t('items', { count: 5 })

Date Formatting

const { formatDate } = useI18n()
formatDate(new Date(), 'long') // "January 19, 2026"
formatDate(new Date(), 'short') // "1/19/26"

Task Localization

Tasks use localeKey for translation:

// Task with localeKey
{ id: '1', localeKey: 'tasks.daily.exercise', name: 'Exercise' }

// Lookup in locale file
{
  "tasks": {
    "daily": {
      "exercise": "Exercise"
    }
  }
}

// Fallback to name if translation missing
const taskName = t(task.localeKey) || task.name

Rules

• Never hardcode user-facing text
• Always provide English fallback
• Use dot notation for nested keys
• Keep keys semantic (describe purpose, not content)
• Group related translations together
• Test RTL languages (Arabic, Hebrew)

Quality Checks

• [ ] All user-facing strings use t()
• [ ] All locales have same key structure
• [ ] Dates formatted with locale
• [ ] Numbers formatted with locale
• [ ] RTL layout works correctly
• [ ] Task localeKeys have translations

Adding New Translations

1. Add key to src/locales/en.json
2. Add translations to all other locale files
3. Use consistent naming convention
4. Test in multiple languages