Drupal 8 add inline JavaScript to a page

Separate JS files are good but in certain cases (e.g. tracking scripts) it might be useful to just add a piece of inline code to a specific page.

This can easily be achieved from a custom module by implementing hook_page_attachments(), checking the page you are on and adding the JS code to the HTML head.

Here is the sample code:

/**
 * 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',
    ];
  }
}

See more:

• hook_page_attachments()
• Drupal::routeMatch()