oliverdavies.uk/source/_daily_emails/2024-08-25.md

---
title: CSS, data attributes and feature flags
date: 2024-08-25
permalink: daily/2024/08/25/css--data-attributes-and-feature-flags
tags:
  - software-development
  - drupal
  - php
  - feature-flags
  - css
cta: ~
snippet: |
  How I combined a feature flag and a data attribute to release some new CSS styles to a project.
---

I recently used [Drupal's Feature Toggle module](https://www.drupal.org/project/feature_toggle) to set a data attribute which enabled some new styling for buttons.

Firstly, within the theme's .theme file, I added this code:

```php
/**
 * Implements hook_preprocess_html().
 */
function mytheme_preprocess_html(array &$variables): void {
  $variables['attributes']['data-use-new-button-styles'] = \Drupal::service('feature_toggle.feature_status')->getStatus('use_the_new_button_styling');
}
```

If the feature toggle is enabled, it adds a `data-use-new-button-styles=""` attribute to the `body` element.

If it is disabled, the attribute is not added, so I can write CSS that's applied when the data attribute is present:

```css
[data-use-new-button-styles] .btn-primary {
  background-color: red;
}
```

In a Tailwind CSS project (this isn't), the same could be achiveable with a custom interaction state - similar to `hover`, `focus` and `active`. Something like `new-button-styles:bg-red-500`.

I like using feature flags and was happy to find a way to use them when adding this new CSS.