效果

代码实现

<template>
  <div>倒计时: {
   
   {
   
    keepTime }}</div>
</template>

<script>
export default {
   
   
  data() {
   
   
    return {
   
   
      keepTime: "",
    };
  },
  created() {
   
   
    this.StartCountDown();
  },
  methods: {
   
   
    // 开始时间
    StartCountDown() {
   
   
      var mydate = new Date();
      mydate.setMinutes(mydate.getMinutes() + 90); //获取后端返回的时间
      this.settime = mydate;
      // 时间到执行停止
      let time = setInterval(() => {
   
   
        if (this.flag == true) {
   
   
          clearInterval(time);
        }
        this.timeDown();
      }, 100);
    },
    // 转换
    timeDown() {
   
   
      const endTime = new Date(this.settime);
      const nowTime = new Date();
      let leftTime = parseInt((endTime.getTime() - nowTime.getTime()) / 1000);
      let d = parseInt(leftTime / (24 * 60 * 60));
      let h = this.formate(parseInt((leftTime / (60 * 60)) % 24));
      let m = this.formate(parseInt((leftTime / 60) % 60));
      let s = this.formate(parseInt(leftTime % 60));
      if (leftTime <= 0) {
   
   
      }
      this.keepTime = `${h}:${m}:${
     
     s}`;
      //计算考试时间
       //var parts = this.keepTime.split(":");
     // var num =  parseInt(parts[0]) * 60 + parseInt(parts[1]) + parseInt(parts[2]) / 60;
     // var minutes = Math.floor(num * 100) / 100;
      //var timelength = this.WhenTime - minutes;//this.WhenTime 为考试时间如：100分钟减去所转换的时间
     // this.timelengthasd = Math.ceil(timelength);//向上取整不到一分钟按一分钟算
    },
    formate(time) {
   
   
      if (time >= 10) {
   
   
        return time;
      } else {
   
   
        return `0${
     
     time}`;
      }
    },
  },
};
</script>

<style>
</style>