Create a custom Twig filter in Drupal 8

Twig can be explanded in many ways, you can add extra tags, filters, tests, oprators, global variables, and functions. You can event extend the parser itself with node visitors.

I am going to show you how to create new custom twig filter in drupal. For example we are going to create a filter to remove a numbers from string, will explain with hello_world module.

Create hello_world folder in modules/custom/folder with following files,

hello_world.info.yml it would contains normal module .info.yml file values. Check here for more detailes.
hello_world.services.yml it would contain following line

services:
  hello_world.twig_extension:
    arguments: ['@renderer']
    class: Drupal\hello_world\TwigExtension\RemoveNumbers
    tags:
      - { name: twig.extension }

src/TwigExtension/RemoveNumbers.php it would contain following in that.

namespace Drupal\hello_world\TwigExtension; 
 
class RemoveNumbers extends \Twig_Extension {    
  /**
   * Generates a list of all Twig filters that this extension defines.
   */
  public function getFilters() {
    return [
      new \Twig_SimpleFilter('removenum', array($this, 'removeNumbers')),
    ];
  }
 
  /**
   * Gets a unique identifier for this Twig extension.
   */
  public function getName() {
    return 'hello_world.twig_extension';
  }
 
  /**
   * Replaces all numbers from the string.
   */
  public static function removeNumbers($string) {
    return preg_replace('#[0-9]*#', '', $string);
  }
}

Enable hello_world module and clear the cache, then you could use the removenum filters in your twig file.

It would remove the all numbers from the string, enjoy with your custom filters!

References

http://leopathu.com/content/create-custom-twig-filter-drupal-8

References

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