<select id="locale-select" onchange="changeLocale(event)">
  <option value="en">English</option>
  <option value="ja">Japanese</option>
</select>

<script>
  function changeLocale(event) {
    document.querySelectorAll('komoju-fields,komoju-picker').forEach(el => {
      el.locale = event.target.value;
    });
  }
</script>