function timeDiff(current, prev) {
  const millisecond = current - prev;
  const second = millisecond / 1000;
  const minute = second / 60;
  const hour = minute / 60;
  const day = hour / 24;
  const week = day / 7;
  const month = week / 4.3;
  const year = month / 12;
  const quarter = year / 4;
  const unitValues = {
    millisecond,
    second,
    minute,
    hour,
    day,
    week,
    month,
    year,
    quarter
  };
  return function diffValueByUnit(unitKey) {
    return unitValues[unitKey];
  };
}


const from = new Date();
from.setDate(from.getDate() - 2);
console.log(from);
const to = new Date(Date.now());
console.log(to);
const diff = timeDiff(from, to);
const result = parseFloat(Math.round(diff("hour")));
console.log(result);
const rtf = new Intl.RelativeTimeFormat("fa");
console.log(rtf.format(result, "hour"));

> Wed Feb 19 2020 02:24:36 GMT+0330 (Iran Standard Time)
> Fri Feb 21 2020 02:24:36 GMT+0330 (Iran Standard Time)
> -48
> "۴۸ ساعت پیش"