Why String Concatenation Is Bad for i18n
One of the most common pitfalls in internationalization (i18n) is string concatenation. It might seem harmless when building UI copy, but once your product goes multilingual, it can turn into a real headache.
Here’s a simple example:
const greeting = "Hello " + userName + "! Welcome back.";
Looks fine in English, right? But when it comes time to translate that into German, Japanese, or Arabic - things start to fall apart.
Language Structure Matters
Languages don’t all follow the same word order. In some, verbs go at the end. In others, adjectives come after nouns. That means this:
"You have " + itemCount + " new messages"
... migh need to be translated as:
- Spanish: "Hay " + itemCount + " mensajes nuevos"
- German: itemCount + " neue Nachrichten haben Sie"
If your text is split into chunks, translators can't rearrange the sentence to follow the grammar of the target language — leading to clunky or incorrect results.
Best Practice: Use Parameterized Strings
Instead of concatenating strings, use placeholders inside complete sentences. Most i18n libraries support this.
Example using i18next:
t("greeting", { userName: "Julia" })
// Output: "Hello Julia! Welcome back."
Translation key:
"greeting": "Hello {{userName}}! Welcome back."
This allows the entire sentence to be translated properly — and naturally — in any language.
Tools That Help
Here are some tools and libraries that make this easy:
- i18next (great for JavaScript/React)
- ICU MessageFormat (widely used and flexible)
- gettext (used in Python, PHP, and C)
- Fluent (developed by Mozilla for expressive translations)
They all support variables, pluralization, and context, without breaking sentences into fragments.
Final Thoughts
String concatenation might be convenient during development — but it doesn’t scale across languages. Using complete, parameterized strings:
- Makes life easier for translators
- Prevents broken grammar and awkward phrasing
- Keeps your code ready for international expansion
Think globally. Code accordingly.
Want help auditing your app or site for i18n readiness?