70 lines
2.3 KiB
JavaScript
70 lines
2.3 KiB
JavaScript
"use strict";
|
|
exports.differenceInMonths = differenceInMonths;
|
|
var _index = require("./compareAsc.js");
|
|
var _index2 = require("./differenceInCalendarMonths.js");
|
|
var _index3 = require("./isLastDayOfMonth.js");
|
|
var _index4 = require("./toDate.js");
|
|
|
|
/**
|
|
* @name differenceInMonths
|
|
* @category Month Helpers
|
|
* @summary Get the number of full months between the given dates.
|
|
*
|
|
* @description
|
|
* Get the number of full months between the given dates using trunc as a default rounding method.
|
|
*
|
|
* @typeParam DateType - The `Date` type, the function operates on. Gets inferred from passed arguments. Allows to use extensions like [`UTCDate`](https://github.com/date-fns/utc).
|
|
*
|
|
* @param dateLeft - The later date
|
|
* @param dateRight - The earlier date
|
|
*
|
|
* @returns The number of full months
|
|
*
|
|
* @example
|
|
* // How many full months are between 31 January 2014 and 1 September 2014?
|
|
* const result = differenceInMonths(new Date(2014, 8, 1), new Date(2014, 0, 31))
|
|
* //=> 7
|
|
*/
|
|
function differenceInMonths(dateLeft, dateRight) {
|
|
const _dateLeft = (0, _index4.toDate)(dateLeft);
|
|
const _dateRight = (0, _index4.toDate)(dateRight);
|
|
|
|
const sign = (0, _index.compareAsc)(_dateLeft, _dateRight);
|
|
const difference = Math.abs(
|
|
(0, _index2.differenceInCalendarMonths)(_dateLeft, _dateRight),
|
|
);
|
|
let result;
|
|
|
|
// Check for the difference of less than month
|
|
if (difference < 1) {
|
|
result = 0;
|
|
} else {
|
|
if (_dateLeft.getMonth() === 1 && _dateLeft.getDate() > 27) {
|
|
// This will check if the date is end of Feb and assign a higher end of month date
|
|
// to compare it with Jan
|
|
_dateLeft.setDate(30);
|
|
}
|
|
|
|
_dateLeft.setMonth(_dateLeft.getMonth() - sign * difference);
|
|
|
|
// Math.abs(diff in full months - diff in calendar months) === 1 if last calendar month is not full
|
|
// If so, result must be decreased by 1 in absolute value
|
|
let isLastMonthNotFull =
|
|
(0, _index.compareAsc)(_dateLeft, _dateRight) === -sign;
|
|
|
|
// Check for cases of one full calendar month
|
|
if (
|
|
(0, _index3.isLastDayOfMonth)((0, _index4.toDate)(dateLeft)) &&
|
|
difference === 1 &&
|
|
(0, _index.compareAsc)(dateLeft, _dateRight) === 1
|
|
) {
|
|
isLastMonthNotFull = false;
|
|
}
|
|
|
|
result = sign * (difference - Number(isLastMonthNotFull));
|
|
}
|
|
|
|
// Prevent negative zero
|
|
return result === 0 ? 0 : result;
|
|
}
|