startCountdown

<p>example1: </p>
<button type="button" @click="() => {
  this.$refs.vac.startCountdown(true)
}">
<vac :left-time="10000" :auto-start="false" ref="vac1">
  <span
    slot="process"
    slot-scope="{ timeObj }">
      {{ timeObj.ceil.s }}
    </span>
    <span slot="finish">Done!</span>
</vac>

<p>example2: </p>
<button type="button" @click="startCountdown">
<vac :left-time="10000" :auto-start="false" ref="vac2" @start="start">
  <span
    slot="process"
    slot-scope="{ timeObj }">
      {{ timeObj.ceil.s }}
    </span>
    <span slot="finish">Done!</span>
</vac>
<script>
export default {
  data() {
    return {}
  },
  methods: {
    startCountdown() {
      const vm = this
      vm.$refs.vac2.startCountdown(true)
    },
    start() {
      console.log('start')
    }
  }
}
</script>