Guid() Javascript

/*Generate four random hex digits.*/
function S4() {
    return (((1 + Math.random()) * 0x10000) | 0).toString(16).substring(1);
};

/*Generate a pseudo-GUID by concatenating random hexadecimal.*/
function guid(format) {

    if (format == "n" || format == "N") {
            return (S4() + S4() + S4() + S4() + S4() + S4() + S4() + S4());
    } else {
            var g = (S4() + S4() + "-" + S4() + "-" + S4() + "-" + S4() + "-" + S4() + S4() + S4());
            if (format == "b" || format == "B") {
                    return "{" + g + "}";
            } else if (format == "p" || format == "P") {
                    return "(" + g + ")";
            }
            return g;
    }
};