vuejs實現倒計時特效

<div id="app" @click="animate">
  <div id="countdown">
    <svg
         :width="size"
         :height="size">
      <circle
              fill="transparent"
              :stroke-width="stroke"
              stroke="#270B58"
              :r="radius"
              :cx="circleOffset"
              :cy="circleOffset"></circle>
      <circle
              class="circle"
              fill="transparent"
              :stroke-width="stroke"
              stroke="#F36F21"
              :r="radius"
              :cx="circleOffset"
              :cy="circleOffset"
              :stroke-dasharray="circumference"
              :stroke-dashoffset="progress"
              stroke-linecap="round"></circle>
    </svg>
    <span>{{ countdown }}</span>
  </div>
</div>

.circle {
  transform: rotate(-90deg);
  transform-origin: 50% 50%;;
}

#countdown {
  display: inline-block;
  position: relative;
}

span {
  position: absolute;
  left: 50%;
  top: 50%;
  transform: translateX(-50%) translateY(-50%);
  font-size: 500px;
  font-family: monospace;
  color: #F36F21;
}

body {
  display: flex;
  justify-content: center;
  align-items: center;
  min-height: 100vh;
  background-color: #43119A;
}

new Vue({
  el: '#app',
  data: {
    size: 600,
    stroke: 30,
    percentage: 100,
    timer: null,
    seconds: 5,
  },
  computed: {
    radius() {
      return (this.size / 2) - (this.stroke / 2);
    },
    circleOffset() {
      return this.size / 2;
    },
    circumference() {
      return this.radius * 2 * Math.PI;
    },
    progress() {
      return this.circumference - this.circumference * this.percentage / 100;
    },
    countdown() {
      return Math.ceil(this.seconds * this.percentage / 100)
    }
  },
  methods: {
    animate() {
      this.timer = setInterval(() => {
        this.percentage -= 1/10;

        if (this.percentage <= 0) {
          clearInterval(this.timer)
          this.percentage = 100;
        }
      }, this.seconds * 1000 / 100 / 10)
    }
  }
})