experimenting with code splitting

src/index.js

@@ -3,22 +3,47 @@
 
 import React from 'react';
 import ReactDOM from 'react-dom';
+
 import { IntlProvider, addLocaleData } from 'react-intl';
-import ruData from 'react-intl/locale-data/ru';
-addLocaleData(ruData);
+const reactIntlLocaleData = {
+  zh: () => import(/* webpackChunkName: "locale_zh" */ 'react-intl/locale-data/zh'), // Chinese simplified.
+  ru: () => import(/* webpackChunkName: "locale_ru" */ 'react-intl/locale-data/ru'), // Russian.
+  en: () => import(/* webpackChunkName: "locale_en" */ 'react-intl/locale-data/en') // English, default.
+};
+
+// import enLocale from 'react-intl/locale-data/en';
+// Russian
+// import ruLocale from 'react-intl/locale-data/ru';
+// Chinese simplified.
+// import zhLocale from 'react-intl/locale-data/zh';
+// addLocaleData([...enLocale, ...ruLocale, ...zhLocale]);
+
 import allMessages from './messages.json';
-
 import TinodeWeb from './views/tinode-web.jsx';
-
 import HashNavigation from './lib/navigation.js';
 
-const {params} = HashNavigation.parseUrlHash(window.location.hash);
+// Detect human language to use in the UI:
+// Check parameters from URL hash #?hl=ru, then browser, then use 'en' as a fallback.
+const { params } = HashNavigation.parseUrlHash(window.location.hash);
 const language = (params && params.hl) ||
   (navigator.languages && navigator.languages[0]) ||
   navigator.language ||
-  navigator.userLanguage;
+  navigator.userLanguage ||
+  'en';
 
-const baseLanguage = language.toLowerCase().split(/[-_]+/)[0];
+console.log("== Got language", language);
+
+// Gets the base language 'en' from a more specific 'en_GB' or 'en-US' as a partial fallback.
+const baseLanguage = language.toLowerCase().split(/[-_]/)[0];
+
+// Dynamically load locale data for the selected language.
+const localeDataLoader =
+  reactIntlLocaleData[language] ||
+  reactIntlLocaleData[baseLanguage] ||
+  reactIntlLocaleData['en'];
+localeDataLoader().then((data) => {
+  addLocaleData(data);
+});
 
 // Try full locale, try locale without region code, fallback to 'en'
 const messages =