Basic ES6 JS for Drupal 8/9 project (module, theme)

myproject.es6.js

(($, Drupal, settings) => {
  Drupal.myproject = {
    preInit(context) {},
    init(settings) {},
    postInit() {},
  };
  Drupal.behaviors.myproject = {
    attach(context, settings) {
    // DOM loaded
      Drupal.myproject.preInit(context);
      $(document, context).once('myprojectInit').each(() => {
      // Page ready -- with single run wrapper
        Drupal.myproject.init(settings);
        $(window).on('load', () => {
        // Page fully loaded
          Drupal.myproject.postInit();
        });
      });
    },
  };
})(jQuery, Drupal, drupalSettings);