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name: translation-strings description: "Use when reviewing a codebase for internationalisation readiness, setting up an i18n library, or preparing strings for a new locale." metadata: category: javascript priority: medium difficulty: intermediate estimatedTime: "30" source: frontendchecklist.io url: https://frontendchecklist.io/rules/javascript/translation-strings

Write internationalisation-friendly translation strings

Naive string concatenation produces untranslatable sentences because word order varies dramatically across languages. A pattern like "Found " + count + " results" cannot be translated correctly into languages where the number appears in a different position or where the noun form changes depending on the count. Bad i18n strings force translators to work around developer mistakes — or simply leave content untranslated.

Quick Reference

• Never concatenate translated strings with variables — use named placeholders
• Use ICU MessageFormat for pluralisation, gender, and select patterns
• Keep translation keys descriptive and scoped to their feature context
• Extract all user-visible strings — do not hardcode any copy in components

Check

Check whether translation strings use proper message formatting with placeholders rather than string concatenation.

Fix

Replace concatenated translation strings with ICU message format patterns and ensure pluralisation is handled via the library, not conditionals.

Explain

Explain why string concatenation breaks translations and how ICU MessageFormat handles variable word order, pluralisation, and gender.

Code Review

Review components and utility functions for hardcoded user-visible strings, string concatenation involving translated text, and missing plural forms.

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For full implementation details, code examples, and framework-specific guidance, see references/rule.md.

Rule page: https://frontendchecklist.io/rules/javascript/translation-strings