favorite.module

<?php

/**
 * Implements template_preprocess_node().
 */
function favorite_preprocess_node(&$variables) {
  $node = $variables['node'];
  if ($variables['view_mode'] == 'full') {
    $variables['#attached']['library'][] = 'favorite/favorite';
    $variables['content']['favorite'] = array(
      '#markup' => '<div id="favorite"></div>',
    );
  }
}