10位是精确到秒，13位是精确到毫秒

    1. const dateFormat = (x) => {
    2.     if(x.toString().length==10) x = x * 1000; // 时间戳位数为10，需要乘以1000
    3.     let date = new Date(x)
    4.     let year = date.getFullYear()
    5.     let month = date.getMonth() + 1
    6.     let day = date.getDate()
    7.     return [year, month, day].map(formatNumber).join('.')
    8. }
    9. const formatNumber = (nth) => {
    10.     let n = nth.toString()
    11.     return nth[1] ? n : 0 + nth
    12. }