vue+moment实现倒计时效果

<!-- 使用计算属性，传入截止日期 -->
<span>{{countDown(endDate)}}</span>

/*引入日期插件*/
import moment from 'moment'
export default {
 data() {
 return {
 now: moment(),
 endDate: '2019-05-07 08:20:00',
 }
 },
 mounted() {
 //定时更新当前时间
 setInterval(()=>{
 this.now = moment()
 },1000),
 //数字前补 0 
 // num传入的数字，n需要的字符长度
 PrefixInteger(num, n) {
 return (Array(n).join(0) + num).slice(-n);
 }
 },
 computed: {
 //计算属性，返回剩余时间
 countDown(){
 return function(endDate) {
 let m1 = this.now
 let m2 = moment(endDate)
 var du = moment.duration(m2 - m1, 'ms'),
 hours = du.get('hours'),
 mins = du.get('minutes'),
 ss = du.get('seconds');
 if(hours<=0 && mins<=0 && ss<=0) {
  return "已超时"
 }else {
  return this.PrefixInteger(hours,2) + ':' + this.PrefixInteger(mins,2) + ':' + this.PrefixInteger(ss,2)
 }
 }
 }
 },
}