<!-- Timer Component -->
<template>
  <span>{{ timer }}</span>
</template>

<script>

  props: {
    startTime: {
      type: String,
      default: '',
    },
  },

  data () {
    return {
      now: Date.now (),
      bias: 0,
    }
  },

  created () {
    this.runTimer ();
  },

  computed: {
    timer () {
      return moment (this.now + this.bias).format ('YYYY/MM/DD HH:mm:ss');
    },
  },

  methods: {
    runTimer () {
      let $vmc = this;
      setInterval (() => $vmc.now = Date.now (), 1000);
    }
  },

  watch: {
    startTime () {
      if (this.start !== '')
        this.bias = moment (this.startTime).valueOf () - this.now;
      else this.bias = 0;
    }
  }

</script>