微信小程序 倒计时

<!-倒计时  wxml-->
<view>{{countDownDay}}天{{countDownHour}}小时{{countDownMinute}}分钟{{countDownSecond}}秒</view>
<!-倒计时  js--> 

Page( {  
  data: {   
    countDownDay: 0,  
    countDownHour: 0,  
    countDownMinute: 0,  
    countDownSecond: 0,  
  }, 
  onLoad: function() {  
    var num = 4085033658;
    this.countDown(num ); 
  },  
  
  // 页面渲染完成后 调用  
  countDown: function (num) {  
    var totalSecond = num - Date.parse(new Date())/1000;  
  
    var interval = setInterval(function () {  
      // 秒数  
      var second = totalSecond;  
  
      // 天数位  
      var day = Math.floor(second / 3600 / 24);  
      var dayStr = day.toString();  
      if (dayStr.length == 1) dayStr = '0' + dayStr;  
  
      // 小时位  
      var hr = Math.floor((second - day * 3600 * 24) / 3600);  
      var hrStr = hr.toString();  
      if (hrStr.length == 1) hrStr = '0' + hrStr;  
  
      // 分钟位  
      var min = Math.floor((second - day * 3600 *24 - hr * 3600) / 60);  
      var minStr = min.toString();  
      if (minStr.length == 1) minStr = '0' + minStr;  
  
      // 秒位  
      var sec = second - day * 3600 * 24 - hr * 3600 - min*60;  
      var secStr = sec.toString();  
      if (secStr.length == 1) secStr = '0' + secStr;  
  
      this.setData({  
        countDownDay: dayStr,  
        countDownHour: hrStr,  
        countDownMinute: minStr,  
        countDownSecond: secStr,  
      });  
      totalSecond--;  
      if (totalSecond < 0) {  
        clearInterval(interval);  
        wx.showToast({  
          title: '活动已结束',  
        });  
        this.setData({  
          countDownDay: '00',  
          countDownHour: '00',  
          countDownMinute: '00',  
          countDownSecond: '00',  
        });  
      }  
    }.bind(this), 1000);  
  },  
 
})