nextcloud/settings/js/isadmin.php

<?php
/**
 * Copyright (c) 2013 Lukas Reschke <lukas@statuscode.ch>
 * This file is licensed under the Affero General Public License version 3 or
 * later.
 * See the COPYING-README file.
 */

// Set the content type to Javascript
header("Content-type: text/javascript");

// Disallow caching
header("Cache-Control: no-cache, must-revalidate"); 
header("Expires: Sat, 26 Jul 1997 05:00:00 GMT"); 

if (OC_User::isAdminUser(OC_User::getUser())) {
	echo("var isadmin = true;");
} else {
	echo("var isadmin = false;");
}