Have a great app? Perfect. Now let’s help the whole world use it.
You’ve built your JavaScript app. It works well, it looks great—but what happens when someone in Japan, Germany, or Brazil opens it and finds everything in English? That’s where localization and internationalization come into the picture.
In this guide, we’ll talk about what software internationalization and localization really mean, and how you can use JavaScript frameworks and libraries to make your app truly global.
We’ll walk you through different tools—from Globalize to i18next and FormatJS—and show you how they work, where they shine, and how to get started.
Let’s break it all down.
What is localization and internationalization?
Before we jump into code or libraries, we need to understand the basic concepts.
Internationalization (i18n)
This is all about preparing your app to support multiple languages, time zones, currencies, and cultures. Think of it like laying the groundwork—you’re building your app in a flexible way so that localization is easy later.
For example:
- You don’t hard-code dates, text, or currency symbols
- You store all strings in one place
- You make sure your app supports RTL (right-to-left) text, like Arabic
Localization (l10n)
This is the actual translation and cultural adaptation. Once your app is internationalized, localization means translating strings, changing date formats (like DD/MM/YYYY vs MM/DD/YYYY), and maybe even swapping images or colors to match a region’s preferences.
In short:
- Internationalization = preparation
- Localization = execution
Now let’s look at how JavaScript fits into this.
JavaScript translation and localization solutions
JavaScript powers a huge chunk of modern apps—especially SPAs (Single Page Applications). But translating JS apps isn’t as simple as using if(lang == ‘en’) blocks everywhere. That quickly turns into a nightmare.
Instead, developers use specialized libraries and frameworks that handle the heavy lifting.
Some of the most popular ones include:
- Globalize
- i18next
- Polyglot.js
- FormatJS
- Lokalise (as a platform to manage translations)
We’ll explore each of these, but first, how do you set up your app to even begin localizing?
Setting up the project for javascript localization
No matter which library you choose, you’ll want to:
1. Externalize your text
Don’t hard-code labels like “Welcome” or “Price” in your app. Instead, move them into a separate file like:
{
“welcome”: “Welcome”,
“price”: “Price”
}
This way, you can create a version of this file for every language.
2. Organize translations
Use folders or namespaces to keep things clean:
/locales
/en
common.json
/fr
common.json
3. Set a default language and fallback
Your app should know which language to load first and what to fall back to if something’s missing.
4. Detect user language
Use browser settings or location to auto-detect the preferred language.
Once that’s ready, it’s time to choose your tool.
JavaScript translation and localization with globalize
Globalize is a powerful library built on top of the Unicode CLDR (Common Locale Data Repository). That means it comes packed with locale data like date formats, currencies, plural rules, and more.
Why use globalize?
- Built for accuracy
- Great for number/date formatting
Maintains performance in large apps
Example Usage:
import Globalize from “globalize”;
Globalize.locale(“fr”);
console.log(Globalize.formatNumber(123456.789)); // Outputs: 123 456,789
It’s especially useful if your app needs complex formatting (like currencies or units) that differ by region. But it doesn’t handle translation strings on its own—you’ll still need another tool for that.
Streamlining JavaScript Translation with i18next
Streamlining JavaScript translation with I18next
i18next is one of the most popular and flexible libraries for localizing JavaScript apps. Whether you’re using plain JavaScript, React, Vue, or even Node.js—i18next works with all of them.
Key Features:
- Loads JSON translation files
- Supports nested keys, pluralization, and fallback languages
- Integrates with React (via react-i18next)
- Language detection plugin
Why people love i18next:
It’s simple to start with, but powerful enough to scale for big projects.
Example Usage:
i18next.init({
lng: “en”,
resources: {
en: { translation: { welcome: “Welcome” } },
fr: { translation: { welcome: “Bienvenue” } },
},
});
console.log(i18next.t(“welcome”)); // Output: Welcome
You can even use it in your HTML:
<h1 data-i18n=”welcome”></h1>
i18next is a great choice for most apps, especially if you’re building something interactive and user-facing.
JavaScript Localization with Polyglot.js
Looking for something super lightweight? Meet Polyglot.js.
It’s not as full-featured as i18next, but for simple apps or prototypes, it does the job.
Best for:
- Small apps or browser extensions
- Quick projects
- Sites that don’t need formatting or complex plural rules
Sample Code:
var polyglot = new Polyglot();
polyglot.extend({
“hello_name”: “Hello, %{name}”
});
console.log(polyglot.t(“hello_name”, { name: “Alex” }));
// Output: Hello, Alex
No huge setup. Just plug it in and start translating.
JavaScript Localization and Message Formatting with FormatJS
FormatJS is a family of libraries, and its most well-known part is React Intl. It’s a favorite for React developers who need solid support for time zones, currencies, and formatting messages.
What it offers:
- ICU Message syntax
- Rich formatting (dates, numbers, plurals)
- Easy integration with React
- Locale data from CLDR
Example with React Intl:
<IntlProvider locale=”en” messages={{ greeting: “Hello {name}” }}>
<FormattedMessage id=”greeting” values={{ name: “Sara” }} />
</IntlProvider>
It’s not limited to React, but that’s where it really shines. If you’re building a global product in React, FormatJS is a strong pick.
Translate JavaScript Apps with Lokalise!
Now, writing translations by hand is fine… until you have 10 languages and 500 strings to manage. That’s when platforms like Lokalise become lifesavers.
What Lokalise does:
- Centralizes your translation files
- Helps teams collaborate (devs + translators)
- Integrates with i18next, FormatJS, and more
- Syncs with GitHub, GitLab, Figma, and Slack
Instead of emailing .json files back and forth, your translator just logs into Lokalise, makes the updates, and it’s synced to your repo automatically.
If your app is growing and you need serious workflow help, Lokalise is worth considering.
Translate and Localize JavaScript Frameworks
Not using plain JavaScript? No problem.
Here’s how localization looks across some common JS frameworks:
React:
- Use react-i18next or React Intl
- A component-based structure makes it easy to plug translations per component
Vue.js:
- Use vue-i18n
- Supports lazy loading and dynamic messages
Angular:
- Built-in i18n support
- Uses XLIFF or JSON for translations
Next.js (React-based):
- Offers built-in internationalized routing
- Works well with i18next or FormatJS
The key idea? Each framework has its own way, but the principles of internationalisation remain the same.
Conclusion: Go Global the Smart Way
Localizing your JavaScript app isn’t just a nice-to-have—it’s essential if you want to connect with users across the globe.
Whether you need lightweight tools like Polyglot.js, scalable solutions like i18next, or advanced formatting with FormatJS, the JavaScript ecosystem has something for every need.
And if you want to stay sane managing hundreds of strings across languages, platforms like Lokalise make that possible without slowing you down.
Final tip?
Start with internationalization from day one. It saves you from a big, messy rewrite later.
FAQs
Q1. What’s the difference between internationalization and localization?
Internationalization is the prep work – structuring your code to support multiple languages. Localization is the actual process of translating and adapting for specific regions.
Q2. Do I need a library for small projects?
If you have a tiny app with only a few strings, a small tool like Polyglot.js is enough. But for anything larger, a proper library (like i18next) saves time and headaches.
Q3. What about right-to-left languages?
Libraries like i18next and FormatJS support RTL out of the box. Just make sure your CSS and layout also handle RTL properly.
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