bc518174
 王天杨
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"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;
}
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