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In Drupal 7, there is a class like path-node-NID (with NID replaced by the node ID of the node being viewed) added to the <body> tag so we can easily add CSS styles to specific nodes. This is missing in Drupal 8.
How can I add the node ID as CSS class to the <body> tag?
In mytheme.theme file: add the below code.
function MYTHEME_preprocess_html(&$variables) {
// Add node ID to the body class.
$node = \Drupal::routeMatch()->getParameter('node');
if (is_object($node)) {
$variables['attributes']['class'][] = 'node-' . $node->id();
}
}
This will add "node-{{nid}}" class in body tag.
Another Option
You can try Node Class module as well.
Node Class is a simple module that allows users to add custom CSS classes to any node through the node/add interface.
mytheme_ in function name with the name of the theme, if the theme name is comets, then : function comets_preprocess_html()
May 17, 2017 at 10:00
$node instanceof \Drupal\node\NodeInterface instead of is_object($node)
Further to the comment made by @hockey2112, the accepted answer throws an error when viewing revisions. The code below is more reliable.
In mytheme.theme file: add the below code.
function mytheme_preprocess_html(&$variables) {
// Add node id to the body class.
$node = \Drupal::routeMatch()->getParameter('node');
if(is_object($node)) {
$variables['attributes']['class'][] = 'node-' . $node->id();
}
}
For those you might still be looking for this on Drupal 9, you may check out this module: https://www.drupal.org/project/body_node_id_class
