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// to add library to all pages

/**
 * Implements hook_page_attachments_alter().
 */
function hook_page_attachments_alter(&$attachments) {
  $attachments['#attached']['library'][] = 'module_name/library_name';
  
  // Remove the stock Drupal favicon if it is present.
  if (isset($attachments['#attached']['html_head_link'])) {
    foreach ($attachments['#attached']['html_head_link'] as $key => $config) {
      if (isset($config[0]['rel']) && $config[0]['rel'] === 'shortcut icon') {
        unset($attachments['#attached']['html_head_link'][$key]);
      }
    }
  }
  
}

/**
 * Implements hook_page_attachments().
 */
function MODULE_NAME_page_attachments(array &$attachments) {
  // You can optionally perform a check to make sure you target a specific page.
  if (\Drupal::routeMatch()->getRouteName() == 'some.route') {
    // Add our JS.
    $attachments['#attached']['html_head'][] = [
      [
        '#tag' => 'script',
        '#attributes' => [
          'type' => 'text/javascript',
        ],
        '#value' => 'console.log("i am here");',
      ],
      'key_for_this_snippet',
    ];
  }
}