mon-entreprise/source/i18n.js

import { I18nextProvider } from 'react-i18next';
import i18next from 'i18next'
import queryString from 'query-string'

import { getIframeOption } from './utils'
import enTranslations from './locales/en.yaml'

let lang = getIframeOption('lang') ||
    queryString.parse(location.search)['lang'] ||
	sessionStorage['lang'] ||
	'fr'

sessionStorage['lang'] = lang

i18next
	.init({
		debug: true,
		lng: lang,
		resources: {
				en: {
			translation: enTranslations
		}}
	}, (err, t) => {
		console.log("Error from i18n load",err,t)
	})

export default lang