Comment convertir des millisecondes en date dans vuejs

export function formatDate (date, fmt) {
  if (/(y+)/.test(fmt)) {
   fmt = fmt.replace(RegExp.$1, (date.getFullYear() + '').substr(4 - RegExp.$1.length));
  }
  let o = {
   'M+': date.getMonth() + 1,
   'd+': date.getDate(),
   'h+': date.getHours(),
   'm+': date.getMinutes(),
   's+': date.getSeconds()
  };
  for (let k in o) {
   if (new RegExp(`(${k})`).test(fmt)) {
    let str = o[k] + '';
    fmt = fmt.replace(RegExp.$1, (RegExp.$1.length === 1) ? str : padLeftZero(str));
   }
  }
  return fmt;
 };

 function padLeftZero (str) {
  return ('00' + str).substr(str.length);
 };

import {formatDate} from '../../common/filters.js'

filters:{
 formatDate(time){
  var data = new Date(time);
  return formatDate(data,'yyyy-MM-dd');
 }
 },

<span>{{item.rateTime | formatDate}}</span>