uni-app里的倒计时期间重置方法

<template>
    <view>
        {{countdown}}
    </view>
</template>

<script>
    export default {
        data() {
            return {
                countdown: '',
                day: '',
                time: '',
                minute: '',
                second: '',
                timer: null //重复执行
            }
        },
        onLoad() {
            this.timer = setInterval(()=>{
                this.showtime()
            },1000)
        },
        methods: {
            showtime () {
                var nowtime = new Date(),  //获取当前时间
                    endtime = new Date("2020/8/8");  //定义结束时间
    
                var lefttime = endtime.getTime() - nowtime.getTime(),  //距离结束时间的毫秒数
                    leftd = Math.floor(lefttime/(1000*60*60*24)),  //计算天数
                    lefth = Math.floor(lefttime/(1000*60*60)%24),  //计算小时数
                    leftm = Math.floor(lefttime/(1000*60)%60),  //计算分钟数
                    lefts = Math.floor(lefttime/1000%60);  //计算秒数
    
                this.countdown =  leftd + "天" + lefth + ":" + leftm + ":" + lefts;  //返回倒计时的字符串
                                
                                this.day =  leftd;//返回天 
                this.time = lefth;//返回时
                this.minute = leftm;//返回分
                this.second = lefts;//返回秒
                
                console.log(this.time)
            }
        }
    }
</script>

<style>

</style>