if (navigator.cookieEnabled) {
    // tutaj mona operowa na cookies
}

----------

var cookieWlaczone = false;
if (typeof document.cookie == "string") {
    if (document.cookie.length == 0) {
        document.cookie = "test";
        cookieWlaczone = (document.cookie == "test");
        document.cookie = "";
    } else {
        cookieWlaczone = true;
    }
}
