GUID(全球唯一标识符)

var guid = function () {
            return 'xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxx'.replace(/[xy]/g, function (c) {
                var r = Math.random() * 16 | 0, v = c == 'x' ? r : (r & 0x3 | 0x8);
                return v.toString(16);
            }).toUpperCase();
        };