Samyk/Evercookie

// https://github.com/samyk/evercookie
// http://samy.pl/evercookie/

 <script type="text/javascript" src="evercookie.js"></script>

    <script>
    var ec = new evercookie();

    // set a cookie "id" to "12345"
    // usage: ec.set(key, value)
    ec.set("id", "12345");

    // retrieve a cookie called "id" (simply)
    ec.get("id", function(value) { alert("Cookie value is " + value) });

    // or use a more advanced callback function for getting our cookie
    // the cookie value is the first param
    // an object containing the different storage methods
    // and returned cookie values is the second parameter
    function getCookie(best_candidate, all_candidates)
    {
        alert("The retrieved cookie is: " + best_candidate + "\n" +
            "You can see what each storage mechanism returned " +
            "by looping through the all_candidates object.");

        for (var item in all_candidates)
            document.write("Storage mechanism " + item +
                " returned: " + all_candidates[item] + "<br>");
    }
    ec.get("id", getCookie);

    // we look for "candidates" based off the number of "cookies" that
    // come back matching since it's possible for mismatching cookies.
    // the best candidate is most likely the correct one
    </script>