JavaScript keySequence

gistfile1.txt

function keySequence(callback) {
    var i = 0;
    var konami = [38, 38, 40, 40, 37, 39, 37, 39, 66, 65];
    $(document).keydown(function (event) {
        if (konami[i] === event.which) {
            i++;
            if (konami.length === i) {
                i = 0;
                callback();
            }
        } else {
            i = +(konami[0] === event.which);
        }
    });
}