Introduction

This is a plugin to use i18next in Fastify, based on i18next-express-middleware.

Getting started

Source can be loaded via npm.

# npm package
$ npm install fastify-i18next

wire up i18next to request object

var i18next = require("i18next");
var fastifyi18next = require("fastify-i18next");
var fastify = require("fastify")({ logger: true });

i18next.use(fastifyi18next.LanguageDetector).init({
  preload: ["en", "de"],
  resources: {
    en: {
      translation: {
        "title": "Hello World!"
      }
    },
    de: {
      translation: {
        "title": "Hallo Welt!"
      }
    }
  },
  ...otherOptions
});

fastify.register(fastifyi18next.plugin, { i18next });

fastify.get('/', async (request, reply) => {
  return request.t('title');
});

const start = async () => {
  try {
    await fastify.listen(3000)
    fastify.log.info(`server listening on ${fastify.server.address().port}`)
  } catch (err) {
    fastify.log.error(err)
    process.exit(1)
  }
}
start()

language detection

Detects user language from current request. Comes with support for:

• path
• cookie
• header
• querystring
• session

Wiring up:

var i18next = require("i18next");
var fastifyi18next = require("fastify-i18next");

i18next.use(fastifyi18next.LanguageDetector).init(i18nextOptions);

As with all modules you can either pass the constructor function (class) to the i18next.use or a concrete instance.

Detector Options

{
  // order and from where user language should be detected
  order: [/*'path', 'session', */ 'querystring', 'cookie', 'header'],

  // keys or params to lookup language from
  lookupQuerystring: 'lng',
  lookupCookie: 'i18next',
  lookupHeader: 'accept-language',
  lookupSession: 'lng',
  lookupPath: 'lng',
  lookupFromPathIndex: 0,

  // cache user language
  caches: false, // ['cookie']

  // optional expire and domain for set cookie
  cookieExpirationDate: new Date(),
  cookieDomain: 'myDomain',
  cookieSecure: true // if need secure cookie
}

Options can be passed in:

preferred - by setting options.detection in i18next.init:

var i18next = require("i18next");
var fastifyi18next = require("fastify-i18next");

i18next.use(fastifyi18next.LanguageDetector).init({
  detection: options
});

on construction:

var fastifyi18next = require("fastify-i18next");
var lngDetector = new fastifyi18next.LanguageDetector(null, options);

via calling init:

var fastifyi18next = require("fastify-i18next");

var lngDetector = new fastifyi18next.LanguageDetector();
lngDetector.init(options);

Adding own detection functionality

interface

module.exports {
  name: 'myDetectorsName',

  lookup: function(req, res, options) {
    // options -> are passed in options
    return 'en';
  },

  cacheUserLanguage: function(req, res, lng, options) {
    // options -> are passed in options
    // lng -> current language, will be called after init and on changeLanguage

    // store it
  }
};

adding it

var i18next = require("i18next");
var fastifyi18next = require("fastify-i18next");

var lngDetector = new fastifyi18next.LanguageDetector();
lngDetector.addDetector(myDetector);

i18next.use(lngDetector).init({
  detection: options
});