i18n.js

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

  
module.exports = (callback) => {
  return new Promise((resolve, reject) => {
    // Initialize i18next
    i18next
      .use(Backend)
      .use(middleware.LanguageDetector)
      .init({
        // debug: true,
        fallbackLng: 'en',
        detection: {
          order: ['querystring', 'cookie', 'header'],
          lookupQuerystring: 'lang',
          caches: ['cookie']
        },
        preload: ['en', 'it'],
        backend: {
          loadPath: __dirname + '/locales/{{lng}}/{{ns}}.json',
        },
          // ...otherOptions
      }, (err, t) => {
        if (err) {
          if (callback) {
            callback(err);
          }
          return reject(err);
        }
        if (callback) {
          callback(null, i18next);
        }
        resolve(i18next);
      });
  });
};