Add a taxonomy ID class to the body tag

Question

I have a taxonomy vocabulary whose various parents and children need to have different styles. I would need the tid of the every taxonomy page to appear as a class in the body tag in order to make CSS selectors.

I tried using How can I dynamically add URL or taxonomy to body class to work out a solution, but it seems to work only for nodes. I get a class called path-taxonomy for every taxonomy term and that's it.

I would prefer not to install any module.

Answer 1

The linked example gets the path. Here better use routing. Check the name of the matched route and then get a parameter which is defined in the route. Normally you use getParameter() to get the loaded entity, in this case it's getRawParameter() for the id:

mytheme.theme:

function mytheme_preprocess_html(&$variables) {
  if (\Drupal::routeMatch()->getRouteName() == 'entity.taxonomy_term.canonical') {
    $variables['term_id'] = \Drupal::routeMatch()->getRawParameter('taxonomy_term');
  }
}

html.html.twig:

{%
  set body_classes = [
    term_id ? 'term-id-' ~ term_id,
  ]
%}
<body{{ attributes.addClass(body_classes) }}>