js 倒计时

var step = 59;
 var _res = setInterval(function () {
                $(".sendSms").attr("disabled", true);//设置disabled属性
                $('.sendSms').text('重新发送' + step + '秒');
                step -= 1;
                if (step <= 0) {
                    $(".sendSms").removeAttr("disabled"); //移除disabled属性
                    $('.sendSms').text('获取验证码');
                    clearInterval(_res);//清除setInterval
                }
            }, 1000);