private function getScriptSrc($callbackName = null)
    {
        $queries = [];

        if ($this->hasLang())
            Arr::set($queries, 'hl', $this->lang);

        Arr::set($queries, 'render', $this->getSiteKey());

        if ($this->hasCallbackName($callbackName))
            Arr::set($queries, 'onload', $callbackName);

        return $this->getClientUrl() . (count($queries) ? '?' . http_build_query($queries) : '');
    }