Method onAttachCallback

/**
 * Method called when asset attached to the Document.
 * Useful for Asset to add a Script options.
 *
 * @param   Document  $doc  Active document
 *
 * @return void
 *
 * @since   4.0.0
 */
public function onAttachCallback(Document $doc)
{
    $app = Factory::getApplication();
    $sessionHandler = $app->get('session_handler', 'database');
    // If the handler is not 'Database', we set a fixed, small refresh value (here: 5 min)
    $refreshTime = 300;
    if ($sessionHandler === 'database') {
        $lifeTime = $app->getSession()->getExpire();
        $refreshTime = $lifeTime <= 60 ? 45 : $lifeTime - 60;
        // The longest refresh period is one hour to prevent integer overflow.
        if ($refreshTime > 3600 || $refreshTime <= 0) {
            $refreshTime = 3600;
        }
    }
    // If we are in the frontend or logged in as a user, we can use the ajax component to reduce the load
    $uri = 'index.php' . ($app->isClient('site') || !Factory::getUser()->guest ? '?option=com_ajax&format=json' : '');
    // Add keepalive script options.
    $doc->addScriptOptions('system.keepalive', array('interval' => $refreshTime * 1000, 'uri' => Route::_($uri)));
}