The I18n

# 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