javascript如何实现时间戳转时间

function getdate() {

            var now = new Date(),

                y = now.getFullYear(),

                m = now.getMonth() + 1,

                d = now.getDate();

            return y + "-" + (m < 10 ? "0" + m : m) + "-" + (d < 10 ? "0" + d : d) + " " + now.toTimeString().substr(0, 8);

        }