Countdown.vue

<template>
    <ul class="vue-countdown">
        <li>
            <p class="digit">{{ days | twoDigits }}</p>
            <p class="text">days</p>
        </li>
        <li>
            <p class="digit">{{ hours | twoDigits }}</p>
            <p class="text">hours</p>
        </li>
        <li>
            <p class="digit">{{ minutes | twoDigits }}</p>
            <p class="text">Min</p>
        </li>
        <li>
            <p class="digit">{{ seconds | twoDigits }}</p>
            <p class="text">Sec</p>
        </li>
    </ul>
</template>

<script>
import Vue from 'vue'

Vue.filter('twoDigits', (value) => {
    if ( value.toString().length <= 1 ) {
        return '0'+value.toString()
    }
    return value.toString()
})
let interval = null;

export default {
    props: ['deadline', 'stop'],
    data() {
        return {
            now: Math.trunc((new Date()).getTime() / 1000),
            diff: 0
        }
    },
    mounted() {

        interval = setInterval(() => {
            this.now = Math.trunc((new Date()).getTime() / 1000)
        }, 1000)

        console.log(interval)
    },
    computed: {
        date() {
            return Math.trunc(Date.parse(this.deadline.replace(/-/g, "/")) / 1000)
        },
        seconds() {
            return Math.trunc(this.diff) % 60
        },

        minutes() {
            return Math.trunc(this.diff / 60) % 60
        },

        hours() {
            return Math.trunc(this.diff / 60 / 60) % 24
        },

        days() {
            return Math.trunc(this.diff / 60 / 60 / 24)
        }
    },
    watch: {
        now(value){
            this.diff = this.date - this.now;
            if(this.diff <= 0 || this.stop){
                this.diff = 0;
                // Remove interval
                clearInterval(interval);
                this.$emit('stop')
            }
        }
    }
}
</script>
<style>
.vue-countdown {
  padding: 0;
  margin: 0;
}
.vue-countdown li {
  display: inline-block;
  margin: 0 8px;
  text-align: center;
  position: relative;
}
.vue-countdown li p {
    margin: 0;
}
.vue-countdown li:after {
  content: ":";
  position: absolute;
  top: 30px;
  right: -13px;
  font-size: 32px;
}
.vue-countdown li:first-of-type {
  margin-left: 0;
}
.vue-countdown li:last-of-type {
  margin-right: 0;
}
.vue-countdown li:last-of-type:after {
  content: "";
}
.vue-countdown .digit {
  font-size: 82px;
  font-weight: 600;
  line-height: 1.4;
  margin-bottom: 0;
}
.vue-countdown .text {
  text-transform: uppercase;
  margin-bottom: 0;
  font-size: 15px;
}
</style>