From https://forum.nette.org/cs/11005-nette-ajax-js-alt-obsluha-pro-ajax-s-jquery?p=5

spinner-nette-ajax.js

(function($, undefined) {
$.nette.ext('spinner', {
        init: function () {
                spinner = $('<div></div>', { id: "ajax-spinner" });
                spinner.appendTo("body");
        },
        before: function (xhr, settings) {
                $("#ajax-spinner").css({
                        visibility: "visible",
                        left: settings.nette.e.pageX,
                        top: settings.nette.e.pageY
                });
        },
        complete: function () {
                $("#ajax-spinner").css({
                        visibility: "hidden"
                });
        }
});
})(jQuery);