AsyncJs.php

<?php

namespace Drupal\advagg_mod\Asset;


/**
 * Add async tag to scripts.
 */
class AsyncJs {
    
    /**
     * Add Async attribute to all external script tags.
     *
     * @param string $content
     *   The response content.
     *
     * @return string
     *   Updated content.
     */
    public function async($content) {
        $pattern = '/<script src=".*"/';
        return preg_replace_callback($pattern, [
            $this,
            'callback',
        ], $content);
    }
    
    /**
     * Callback to replace individual stylesheet links.
     *
     * @param array $matches
     *   Array from matches from preg_replace_callback.
     *
     * @return string
     *   Updated html string.
     */
    protected function callback(array $matches) {
        return "{$matches[0]} async";
    }

}