days360.js

import parsebool from "./parsebool";
import parsedate from "./parsedate";

export default function days360(start_date, end_date, method) {
  method = parsebool(method);
  start_date = parsedate(start_date);
  end_date = parsedate(end_date);

  if (start_date instanceof Error) {
    return start_date;
  }
  if (end_date instanceof Error) {
    return end_date;
  }
  if (method instanceof Error) {
    return method;
  }
  var sm = start_date.getMonth();
  var em = end_date.getMonth();
  var sd, ed;
  if (method) {
    sd = start_date.getDate() === 31 ? 30 : start_date.getDate();
    ed = end_date.getDate() === 31 ? 30 : end_date.getDate();
  } else {
    var smd = new Date(start_date.getFullYear(), sm + 1, 0).getDate();
    var emd = new Date(end_date.getFullYear(), em + 1, 0).getDate();
    sd = start_date.getDate() === smd ? 30 : start_date.getDate();
    if (end_date.getDate() === emd) {
      if (sd < 30) {
        em++;
        ed = 1;
      } else {
        ed = 30;
      }
    } else {
      ed = end_date.getDate();
    }
  }
  return (
    360 * (end_date.getFullYear() - start_date.getFullYear()) +
    30 * (em - sm) +
    (ed - sd)
  );
}