JsOptimizer.php

<?php

namespace Drupal\Core\Asset;

use Drupal\Component\Utility\Unicode;

/**
 * Optimizes a JavaScript asset.
 */
class JsOptimizer implements AssetOptimizerInterface {
    
    /**
     * {@inheritdoc}
     */
    public function optimize(array $js_asset) {
        if ($js_asset['type'] !== 'file') {
            throw new \Exception('Only file JavaScript assets can be optimized.');
        }
        if (!$js_asset['preprocess']) {
            throw new \Exception('Only file JavaScript assets with preprocessing enabled can be optimized.');
        }
        // If a BOM is found, convert the file to UTF-8, then use substr() to
        // remove the BOM from the result.
        $data = file_get_contents($js_asset['data']);
        if ($encoding = Unicode::encodingFromBOM($data)) {
            $data = mb_substr(Unicode::convertToUtf8($data, $encoding), 1);
        }
        elseif (isset($js_asset['attributes']['charset'])) {
            $data = Unicode::convertToUtf8($data, $js_asset['attributes']['charset']);
        }
        // No-op optimizer: no optimizations are applied to JavaScript assets.
        return $data;
    }
    
    /**
     * Processes the contents of a javascript asset for cleanup.
     *
     * @param string $contents
     *   The contents of the javascript asset.
     *
     * @return string
     *   Contents of the javascript asset.
     */
    public function clean($contents) {
        // Remove JS source and source mapping urls or these may cause 404 errors.
        $contents = preg_replace('/\\/\\/(#|@)\\s(sourceURL|sourceMappingURL)=\\s*(\\S*?)\\s*$/m', '', $contents);
        return $contents;
    }

}