История изменений

(function poll() {
    setTimeout(function () {
        $.getJSON('/your-url', function (e) {
            // do what you need
            poll();
        });
    }, 334 /*ms*/);
}());

(function poll() {
    setTimeout(function () {
        $.getJSON('/echo/json', function (e) {
            // do what you need
            poll();
        });
    }, 334 /*ms*/);
}());