title: How to correctly polyfill Intl locale data
body: <p>I'm a little confused about how to actually polyfill certain common locale data (CLDR) from the <a href="https://github.com/andyearnshaw/Intl.js/#locale-data" rel="nofollow noreferrer">Intl polyfill</a>.</p>
  
  <p>What I understand so far is the following (please correct me if I'm wrong here):</p>
  
  <ul>
  <li>Modern browsers ship the locale data themselves (no polyfill needed whatsoever)</li>
  <li><code>Intl.min</code> comes without any locale data</li>
  <li><code>Intl.complete</code> comes with all locale data from <code>intl/locale-data</code> bundled</li>
  </ul>
  
  <p>Since we only need to support some locales (lets say <code>en</code> &amp; <code>de</code>) it'd be wise to only bundle <code>Intl.min</code> and dynamically load the CLDR when needed (on app start or when the user changes the language).</p>
  
  <p>How do I dynamically load the CLDR when needed &amp; how do I add it to <code>Intl</code>?</p>
  
  <p>I've got <code>aurelia-i18n</code> &amp; <code>i18next</code> already set up so that they load our custom translations only when needed using the <code>i18next-xhr-backend</code>. Can I somehow hook into this &amp; also load the needed locale from the <code>Intl</code> polyfill?</p>
  
  <ul>
  <li>If so, how do I do this and how do I check beforehand on whether it is necessary or not (new browsers don't need it and it could already be loaded)?</li>
  <li>Am I correct in the assumption that I don't have to manually add the locale after it has been loaded since it does this itself (e.g. <code>intl/locale-data/jsonp/en.js</code> starts with <code>IntlPolyfill.__addLocaleData(...);</code>)?</li>
  </ul>