时间倒计时操作

    var time = 1800; //30分钟换算成1800秒
    this.timer = setInterval(() => {
      if (time > 0) {
           time = time - 1;
            var minute = parseInt(time / 60);
            var second = parseInt(time % 60);
            let title='倒计时：' + minute.toString().padStart(2,'0') + ':' +  second.toString().padStart(2,'0')
         } else {
             clearInterval(this.timer)
          }
    }, 1000);