public function minifyJs($sourceFileList, $targetFile) {
        $sourceFileList = (array)$sourceFileList;
        $sourceFileList = array_map(array($this, '_createFullPath'), $sourceFileList);
        $sourceFileList = implode(' ', $sourceFileList);
        $targetFile = $this->_createFullPath($targetFile);

        $uglifyJsCommand = 'uglifyjs '.$sourceFileList.' -o '.$targetFile.' -c -m';
        `$uglifyJsCommand`;
    }