How to use nested locale folder for i18next

When using i18next for internationalization, organizing and managing translation files is critical, especially when the application supports multiple languages and region-specific variants. Implementing nested locale folders helps organize these files more effectively. Below are the steps to implement this:

1. Design Folder Structure

First, design a clear folder structure to store translation files for various languages and regions. For example, create a top-level folder for each language and subfolders for each region within it. Here is an example structure:

shell
/locales
  /en
    translation.json
    /GB
      translation.json
    /US
      translation.json
  /de
    translation.json
    /DE
      translation.json

In this structure, en, de, etc. folders store general language translations, while subfolders like GB, US, DE store region-specific translation details.

2. Configure i18next

Next, configure i18next correctly to recognize and use this folder structure. This typically involves setting the backend option to specify how to load translation files. For example, using the i18next-fs-backend or similar backend plugin, configure it as follows:

javascript
const i18next = require('i18next');
const Backend = require('i18next-fs-backend');

i18next.use(Backend).init({
  lng: 'en', // Default language
  fallbackLng: 'en',
  backend: {
    loadPath: './locales/{{lng}}/{{ns}}.json',
  },
});

In this configuration, loadPath uses variables like {{lng}} and {{ns}}, which i18next automatically fills based on the current language and namespace. Ensure your file naming and folder structure match the pattern specified in loadPath.

3. Dynamically Load Region-Specific Files

In some cases, you may need to dynamically load region-specific translation files based on the user's location. Achieve this by adding logic to the language change function, for example:

javascript
function changeLanguage(lng, region) {
  const language = region ? `${lng}-${region}` : lng;
  i18next.changeLanguage(language, (err, t) => {
    if (err) return console.error('Something went wrong loading', err);
    console.log('language changed');
  });
}

In this function, the region parameter allows you to specify a particular region, and the function requests the corresponding translation file.

4. Test and Validate

Finally, thoroughly test your translation and file loading logic to ensure translations load correctly for all expected language and region combinations. This may include unit tests and end-to-end tests.

By using this nested folder structure, you can make your internationalization logic clearer and easier to manage. It also provides greater flexibility to support more languages and region-specific variants.