strapi-plugin-i18n/admin/src/utils/getInitialLocale.js

This plugin enables to create, to read and to update content in different languages, both from the Admin Panel and from the API

import getLocaleFromQuery from './getLocaleFromQuery';

const getInitialLocale = (query, locales = []) => {
  const localeFromQuery = getLocaleFromQuery(query);

  if (localeFromQuery) {
    return locales.find(locale => locale.code === localeFromQuery);
  }

  // Returns the default locale when nothing is in the query
  return locales.find(locale => locale.isDefault);
};

export default getInitialLocale;