datedif.js

import parsedate from "./parsedate";
import isNaN from "./isnan";

export default function datedif(start_date, end_date, unit) {
  var second = 1000,
    minute = second * 60,
    hour = minute * 60,
    day = hour * 24,
    week = day * 7;
  (start_date = parsedate(start_date)), (end_date = parsedate(end_date));

  var timediff = end_date - start_date;
  if (isNaN(timediff)) return NaN;

  switch (unit) {
    case "Y":
      return end_date.getFullYear() - start_date.getFullYear();
    case "M":
      return (
        end_date.getFullYear() * 12 +
        end_date.getMonth() -
        (start_date.getFullYear() * 12 + start_date.getMonth())
      );
    case "W":
      return Math.floor(timediff / week);
    case "D":
      return Math.floor(timediff / day);
    case "MD":
      return end_date.getdate() - start_date.getdate();
    case "YM":
      return end_date.getMonth() - start_date.getMonth();
    case "YD":
      return new error("NOT IMPLEMENTED");
    default:
      return undefined;
  }
}