js生成guid方法

  function guidGenerator() {
            var S4 = function () {
                return (((1 + Math.random()) * 0x10000) | 0).toString(16).substring(1);
            };
            return (S4() + S4() + "-" + S4() + "-" + S4() + "-" + S4() + "-" + S4() + S4() + S4());
        }