获取验证码60秒等待

var countdown = 60;
        function settime() {
            var obj = document.getElementById("btnVer");
            if (countdown == 0) {
                obj.removeAttribute("disabled");
                obj.value = "获取验证码";
                countdown = 60;
                return;
            } else {
                obj.setAttribute("disabled", true);
                obj.value = "重新发送(" + countdown + ")";
                countdown--;
            }
            setTimeout(function () {
                settime()
            }
            , 1000)
        }