Javascript fallback for broken default values in OctoberCMS' Repeater fields

fields.yaml

fields:
    extra_information:
        type: repeater
        form:
            fields:
                foobar:
                    label: Foobar
                    type: text
                    # This won't work:
                    default: lorem ipsum
                    attributes:
                        # Which is why we use this attribute:
                        data-default-value: lorem ipsum

Plugin.php

<?php
class Plugin extends PluginBase
{
  public function boot()
  {
    Event::listen('backend.page.beforeDisplay', function($controller, $action, $params) {
      $controller->addJs('/plugins/grrr/flexiblepages/assets/javascript/repeater.js');
    });
  }
}

repeater.js

$(function() {
  if (!$.fn.fieldRepeater) {
    return;
  }

  const fixDefaultValues = $item => {
    const $inputs = $item.find("[data-default-value]");
    $inputs.each(function() {
      const $input = $(this);
      if (!$input.val()) {
        $input.val($input.data("default-value"));
      }
    });
  };

  // Listen for newly added list-items
  const observer = new MutationObserver(mutations => {
    mutations
      .filter(m => m.type === "childList")
      .map(m =>
        Array.from(m.addedNodes).filter(n => n.nodeType === 1).forEach(x => 
          fixDefaultValues($(x));
        ));
  });

  const config = { attributes: false, childList: true, characterData: false };
  observer.observe($(".field-repeater-items").get(0), config);
});