手机短信验证码的定时器

//            验证码计时器
            var countdown = 60;
            function settime() {
                if(countdown == 0) {
                    $('.settime').removeAttr("disabled")
                    $('.settime').val("获取验证码")
                    countdown = 60;
                    return false;
                } else {
                    $('.settime').attr("disabled", "disabled")
                    $('.settime').val("重新发送(" + countdown + ")")
                    countdown--;
                }
                var tt = setTimeout(function() {
                    settime();
                }, 1000);
            }
            //            调用
            setTimeout(function() {
                settime();
            }, 1000);