Getting Started Internationalizing (i18n) with Intlayer and React Create App

What is Intlayer?

Intlayer is an innovative, open-source internationalization (i18n) library designed to simplify multilingual support in modern web applications.

With Intlayer, you can:

Easily manage translations using declarative dictionaries at the component level.
Dynamically localize metadata, routes, and content.
Ensure TypeScript support with autogenerated types, improving autocompletion and error detection.
Benefit from advanced features, like dynamic locale detection and switching.

Step-by-Step Guide to Set Up Intlayer in a React Application

Step 1: Install Dependencies

Install the necessary packages using npm:

npm install intlayer react-intlayer

yarn add intlayer react-intlayer

pnpm add intlayer react-intlayer

Step 2: Configuration of your project

Create a config file to configure the languages of your application:

// intlayer.config.ts

import { Locales, type IntlayerConfig } from "intlayer";

const config: IntlayerConfig = {
  internationalization: {
    locales: [
      Locales.ENGLISH,
      Locales.FRENCH,
      Locales.SPANISH,
      // Your other locales
    ],
    defaultLocale: Locales.ENGLISH,
  },
};

export default config;

To see all available parameters, refer to the configuration documentation here.

Step 3: Integrate Intlayer in Your CRA Configuration

Change your scripts to use react-intlayer

  "scripts": {
    "build": "react-intlayer build",
    "start": "react-intlayer start",
    "transpile": "intlayer build"
  },

Note: react-intlayer scripts are based on craco. You can also implement your own setup based on the intlayer craco plugin. See example here.

Step 4: Declare Your Content

Create and manage your content dictionaries:

// src/app.content.tsx
import { t, type DeclarationContent } from "intlayer";
import { type ReactNode } from "react";

const appContent = {
  key: "app",
  content: {
    getStarted: t<ReactNode>({
      en: (
        <>
          Edit <code>src/App.tsx</code> and save to reload
        </>
      ),
      fr: (
        <>
          Éditez <code>src/App.tsx</code> et enregistrez pour recharger
        </>
      ),
      es: (
        <>
          Edita <code>src/App.tsx</code> y guarda para recargar
        </>
      ),
    }),
    reactLink: {
      href: "https://reactjs.org",
      content: t({
        en: "Learn React",
        fr: "Apprendre React",
        es: "Aprender React",
      }),
    },
  },
} satisfies DeclarationContent;

export default appContent;

See how to declare your Intlayer declaration files.

Step 5: Utilize Intlayer in Your Code

Access your content dictionaries throughout your application:

import logo from "./logo.svg";
import "./App.css";
import { IntlayerProvider, useIntlayer } from "react-intlayer";
import { LocaleSwitcher } from "./components/LangSwitcherDropDown";

function AppContent() {
  const content = useIntlayer("app");

  return (
    <header className="App-header">
      <img src={logo} className="App-logo" alt="logo" />

      {content.getStarted}
      <a
        className="App-link"
        href={content.reactLink.href.value}
        target="_blank"
        rel="noopener noreferrer"
      >
        {content.reactLink.content}
      </a>
    </header>
  );
}

function App() {
  return (
    <IntlayerProvider>
      <div className="App">
        {/* To use the useIntlayer hook properly, you should access your data in a children component */}
        <AppContent />
      </div>
      <div className="absolute bottom-5 right-5 z-50">
        <LocaleSwitcher />
      </div>
    </IntlayerProvider>
  );
}

export default App;

Note: If you want to use your content in a string attribute, such as alt, title, href, aria-label, etc., you must call the value of the function, like:
<img src={content.image.src.value} alt={content.image.value} />

(Optional) Step 6: Change the language of your content

To change the language of your content, you can use the setLocale function provided by the useLocale hook. This function allows you to set the locale of the application and update the content accordingly.

import { Locales } from "intlayer";
import { useLocale } from "react-intlayer";

const LocaleSwitcher = () => {
  const { setLocale } = useLocale();

  return (
    <button onClick={() => setLocale(Locales.English)}>
      Change Language to English
    </button>
  );
};

(Optional) Step 7: Add localized Routing to your application

The purpose of this step is to make unique routes for each language. This is useful for SEO and SEO-friendly URLs. Example:

// /dashboard
// /es/dashboard
// /fr/dashboard

By default, the routes are not prefixed for the default locale. If you want to prefix the default locale, you can set the middleware.prefixDefault option to true in your configuration. See the configuration documentation for more information.

To add localized routing to your application, you can create a LocaleRouter component that wraps your application's routes and handles locale-based routing. Here is an example using React Router:

// Importing necessary dependencies and functions
import { Locales, getConfiguration, getPathWithoutLocale } from "intlayer"; // Utility functions and types from 'intlayer'
import { FC, PropsWithChildren } from "react"; // React types for functional components and props
import { IntlayerProvider } from "react-intlayer"; // Provider for internationalization context
import {
  BrowserRouter,
  Routes,
  Route,
  useParams,
  Navigate,
  useLocation,
} from "react-router-dom"; // Router components for managing navigation

// Destructuring configuration from Intlayer
const { internationalization, middleware } = getConfiguration();
const { locales, defaultLocale } = internationalization;

/**
 * A component that handles localization and wraps children with the appropriate locale context.
 * It manages URL-based locale detection and validation.
 */
const AppLocalized: FC<PropsWithChildren> = ({ children }) => {
  const path = useLocation().pathname; // Get the current URL path
  const { locale } = useParams<{ locale: Locales }>(); // Extract the locale parameter from the URL

  // Determine the current locale, falling back to the default if not provided
  const currentLocale = locale ?? defaultLocale;

  // Remove the locale prefix from the path to construct a base path
  const pathWithoutLocale = removeLocaleFromUrl(
    path // Current URL path
  );

  /**
   * If middleware.prefixDefault is true, the default locale should always be prefixed.
   */
  if (middleware.prefixDefault) {
    // Validate the locale
    if (!locale || !locales.includes(locale)) {
      // Redirect to the default locale with the updated path
      return (
        <Navigate
          to={`/${defaultLocale}/${pathWithoutLocale}`}
          replace // Replace the current history entry with the new one
        />
      );
    }

    // Wrap children with the IntlayerProvider and set the current locale
    return (
      <IntlayerProvider locale={currentLocale}>{children}</IntlayerProvider>
    );
  } else {
    /**
     * When middleware.prefixDefault is false, the default locale is not prefixed.
     * Ensure that the current locale is valid and not the default locale.
     */
    if (
      currentLocale.toString() !== defaultLocale.toString() &&
      !locales
        .filter(
          (locale) => locale.toString() !== defaultLocale.toString() // Exclude the default locale
        )
        .includes(currentLocale) // Check if the current locale is in the list of valid locales
    ) {
      // Redirect to the path without locale prefix
      return <Navigate to={pathWithoutLocale} replace />;
    }

    // Wrap children with the IntlayerProvider and set the current locale
    return (
      <IntlayerProvider locale={currentLocale}>{children}</IntlayerProvider>
    );
  }
};

/**
 * A router component that sets up locale-specific routes.
 * It uses React Router to manage navigation and render localized components.
 */
export const LocaleRouter: FC<PropsWithChildren> = ({ children }) => (
  <BrowserRouter>
    <Routes>
      <Route
        // Route pattern to capture the locale (e.g., /en/, /fr/) and match all subsequent paths
        path="/:locale/*"
        element={<AppLocalized>{children}</AppLocalized>} // Wraps children with locale management
      />

      {
        // If prefixing the default locale is disabled, render the children directly at the root path
        !middleware.prefixDefault && (
          <Route
            path="*"
            element={<AppLocalized>{children}</AppLocalized>} // Wraps children with locale management
          />
        )
      }
    </Routes>
  </BrowserRouter>
);

(Optional) Step 8: Change the URL when the locale changes

To change the URL when the locale changes, you can use the onLocaleChange prop provided by the useLocale hook. In parallel, you can use the useLocation and useNavigate hooks from react-router-dom to update the URL path.

import { Locales, getLocalizedUrl } from "intlayer";
import { useLocale } from "react-intlayer";
import { useLocation, useNavigate } from "react-router-dom";

const LocaleSwitcher = () => {
  const location = useLocation(); // Get the current URL path. Example: /fr/about
  const navigate = useNavigate();

  const changeUrl = (locale: Locales) => {
    // Construct the URL with the updated locale
    // Example: /es/about with the locale set to Spanish
    const pathWithLocale = getLocalizedUrl(location.pathname, locale);

    // Update the URL path
    navigate(pathWithLocale);
  };

  const { setLocale } = useLocale({
    onLocaleChange: changeUrl,
  });

  return (
    <button onClick={() => setLocale(Locales.English)}>
      Change Language to English
    </button>
  );
};

Configure TypeScript

Intlayer use module augmentation to get benefits of TypeScript and make your codebase stronger.

alt text

Ensure your TypeScript configuration includes the autogenerated types.

// tsconfig.json

{
  // your custom config
  include: [
    "src",
    "types", // <- Include the auto generated types
  ],
}

Git Configuration

It is recommended to ignore the files generated by Intlayer. This allows you to avoid committing them to your Git repository.

To do this, you can add the following instructions to your .gitignore file:

# Ignore the files generated by Intlayer
.intlayer

If you have an idea for improving this documentation, please feel free to contribute by submitting a pull request on GitHub.

GitHub link to the documentation