Domain name as a class name

function themeName_preprocess_html(&$variables) {
        // Get the base URL
        $base_path = Url::fromRoute('<front>', [], ['absolute' => TRUE])->toString();
        // Remove the https protocal from url
        $client_base_name = explode("//", $base_path);
        // Pass the base name without https and get the first name from the url
        $client_name = explode(".",$client_base_name[1]);
        // First name of the site before first dot will be the class name
        $class_name = $client_name[0];
        $variables['attributes']['class'][] = $class_name;
}