YourCuteDrupalController.php

<?php
/**
   * Render.
   *
   * @param $course_code
   *
   * @return array
   *   Returns a renderable array.
   */
  public function render($course_code) {
    return [
      '#type' => 'markup',
      '#markup' => '<div id="root"></div>',
      '#attached' => [
        'drupalSettings' => [
          'course_code' => $course_code,
        ],
        'library' => [
          'YOURLIBRARY.NAME',
        ],
      ],
    ];
  }