发送验证码，倒计时处理

    var isvalidSend = true;
    //点击 <发送验证码> 按钮
    function bindSmsCode() {
        $("#btnSendSmsAuthCode").on("click", function () {         
            if (!isvalidSend) {
                return;
            }        
            var self = this;
            //手机号验证
            sendCode(phone);
        });
    };

    //辅助方法-发送验证码
    function sendCode(_phonenum) {
        isvalidSend = false;    
        _Ajax('xx',
          {
              Mobile: _phonenum,
          }, function (res) {
              if (发送失败判断) {
                  isvalidSend = true;
                  return;
              }
              countDown();
            }, function (a, b, c) {
              isvalidSend = true;return;
          });
    };        
    //辅助方法-验证码倒计时
    function countDown() {       
        var startTime = 60;
        var boxtime;
        var showBtn = $('#btnSendSmsAuthCode');
        function time() {
            startTime--;
            if (startTime == 0) {
                clearInterval(boxtime);                
                startTime = 60;
                showBtn.val("发送验证码");
                isvalidSend = true;
                return;
            }
            showBtn.val("重新发送(" + startTime + ")");
         } 
        boxtime = window.setInterval(time, 1000);   
    };