Using #attached only when neededfor Drupal 8 , 9 , 10 , and 11

Introduction

Following our previous lesson on creating minimal libraries in .libraries.yml, we now focus on efficiently utilizing these resources with the #attached property in Drupal. This lesson discusses how to conditionally attach assets using #attached, minimizing unnecessary loading to enhance your site’s performance.

Understanding #attached in Drupal

In Drupal, #attached allows developers to bind JavaScript, CSS, and libraries to a render array, ensuring assets are loaded only when required. This feature aids in avoiding bloated files and unnecessary HTTP requests, helping to streamline the performance of your webpages.

Benefits of Using #attached Efficiently

• Performance Enhancement: Only the required resources are loaded, thereby reducing the page load time.
• Resource Optimization: Helps in managing dependencies precisely, loading assets just in time for when they are needed.
• Improved User Experience: Speeding up page loads and reducing unnecessary noise leads to a smoother navigation experience for users.

Implementing Conditional Attachment in Drupal

Below is a step-by-step guide on how to use the #attached property efficiently:

1. Identify Areas Requiring Conditional Assets

   Determine which pages or components require specific resources. For instance, analytics scripts may not be necessary on non-critical internal pages.

2. Attach Resources Conditionally

   Within your custom module or theme’s preprocessing function, use #attached to conditionally attach these libraries:

   
   function my_module_preprocess_node(&$variables) {
     // Check for specific node content type.
     if ($variables['node']->getType() == 'custom_type') {
       $variables['#attached']['library'][] = 'my_module/custom_library';
     }
   }
   

   This example ensures that custom_library is only loaded for nodes of type custom_type.

3. Use Conditional Logic

   Leverage PHP logic to determine when specific resources are necessary. For example, add a library only if a certain condition is met:

   
   function my_module_preprocess_page(&$variables) {
     // Attach admin styles only for admin pages.
     if (\Drupal::currentUser()->hasPermission('administer site configuration')) {
       $variables['#attached']['library'][] = 'my_module/admin_styles';
     }
   }
   

Testing and Validation

• Cache Clearing: Use drush cr to ensure that your changes take effect after modifying the theme or module.
• Performance Testing: Analyze your site with tools like Google Lighthouse or GTmetrix to assess load improvements.
• Functionality Verification: Navigate through your site to ensure that all necessary styles and scripts load correctly and that conditional logic operates as expected.

Considerations and Best Practices

• Keep Logic Simple: Avoid over-complicating conditions as this can lead to maintenance difficulties and potential performance issues.
• Document Changes: Keep clear documentation, detailing where and why each resource is conditionally attached, to facilitate future audits and modifications.
• Regular Monitoring: Consistently review resource loading and performance metrics as the site grows or changes are implemented.

Conclusion

Adopting a strategy where #attached is utilized only when necessary ensures your Drupal site operates efficiently, reducing load times and bandwidth usage. This approach not only optimizes performance but also contributes to a better user experience by delivering content swiftly.

Next in the Series

The upcoming lesson will focus on Avoiding Unnecessary Library Dependencies. This topic will cover how to streamline your code and dependencies for even stronger performance gains. Stay tuned!