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media/system/js/keepalive.js

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+/**
+ * @copyright   (C) 2018 Open Source Matters, Inc. <https://www.joomla.org>
+ * @license     GNU General Public License version 2 or later; see LICENSE.txt
+ */
+
+/**
+ * Keepalive javascript behavior
+ *
+ * Used for keeping the session alive
+ *
+ * @package  Joomla.JavaScript
+ * @since    3.7.0
+ */
+if (!window.Joomla) {
+  throw new Error('Joomla API was not properly initialised');
+}
+const keepAliveOptions = Joomla.getOptions('system.keepalive');
+const keepAliveInterval = keepAliveOptions && keepAliveOptions.interval ? parseInt(keepAliveOptions.interval, 10) : 45 * 1000;
+let keepAliveUri = keepAliveOptions && keepAliveOptions.uri ? keepAliveOptions.uri.replace(/&amp;/g, '&') : '';
+
+// Fallback in case no keepalive uri was found.
+if (keepAliveUri === '') {
+  const systemPaths = Joomla.getOptions('system.paths');
+  keepAliveUri = `${systemPaths ? `${systemPaths.root}/index.php` : window.location.pathname}?option=com_ajax&format=json`;
+}
+setInterval(() => fetch(keepAliveUri, {
+  method: 'POST'
+}), keepAliveInterval);