// excel读取2018/01/01这种时间格式是会将它装换成数字类似于46254.1545151415 numb是传过来的整数数字，format是之间间隔的符号

function formatDate(numb) {

  if (numb > 0) { //  先解析时间

      const time = new Date((numb - 1) * 24 * 3600000 + 1);

      let h = time.getHours() + 16;

      let yeraData = new Date(1900, 0, numb - 1)

      let year = yeraData.getFullYear();

      let month = yeraData.getMonth() + 1

      month = month < 10 ? '0' + month : month;

      let day = yeraData.getDate()

      day = day < 10 ? '0' + day : day;

      if (h > 23) {

          h = h - 24;

      }

      let m = time.getMinutes() < 10 ? "0" + time.getMinutes() : time.getMinutes();

      let s = time.getSeconds() < 10 ? "0" + time.getSeconds() : time.getSeconds();

      return `${year}/${month}/${day}`;

  } else {

      // console.log(numb)

      return '非法日期格式';

  }

}
export {
  formatDate
}　　
// console.log(formatDate(42618, '/')) // 2016-9-5

或者

    formatDate(numb, format) {
      const time = new Date((numb - 1) * 24 * 3600000 + 1)
      time.setYear(time.getFullYear() - 70)
      const year = time.getFullYear() + ''
      const month = time.getMonth() + 1 + ''
      const date = time.getDate() - 1 + ''
      if (format && format.length === 1) {
        return year + format + month + format + date
      }
      return year + (month < 10 ? '0' + month : month) + (date < 10 ? '0' + date : date)
    },　　
console.log(formatDate(42618, '/')) // 2016-9-5