You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
44 lines
1.8 KiB
44 lines
1.8 KiB
import toDate from '../toDate/index.js';
|
|
import differenceInCalendarYears from '../differenceInCalendarYears/index.js';
|
|
import compareAsc from '../compareAsc/index.js';
|
|
import requiredArgs from '../_lib/requiredArgs/index.js';
|
|
/**
|
|
* @name differenceInYears
|
|
* @category Year Helpers
|
|
* @summary Get the number of full years between the given dates.
|
|
*
|
|
* @description
|
|
* Get the number of full years between the given dates.
|
|
*
|
|
* ### v2.0.0 breaking changes:
|
|
*
|
|
* - [Changes that are common for the whole library](https://github.com/date-fns/date-fns/blob/master/docs/upgradeGuide.md#Common-Changes).
|
|
*
|
|
* @param {Date|Number} dateLeft - the later date
|
|
* @param {Date|Number} dateRight - the earlier date
|
|
* @returns {Number} the number of full years
|
|
* @throws {TypeError} 2 arguments required
|
|
*
|
|
* @example
|
|
* // How many full years are between 31 December 2013 and 11 February 2015?
|
|
* var result = differenceInYears(new Date(2015, 1, 11), new Date(2013, 11, 31))
|
|
* //=> 1
|
|
*/
|
|
|
|
export default function differenceInYears(dirtyDateLeft, dirtyDateRight) {
|
|
requiredArgs(2, arguments);
|
|
var dateLeft = toDate(dirtyDateLeft);
|
|
var dateRight = toDate(dirtyDateRight);
|
|
var sign = compareAsc(dateLeft, dateRight);
|
|
var difference = Math.abs(differenceInCalendarYears(dateLeft, dateRight)); // Set both dates to a valid leap year for accurate comparison when dealing
|
|
// with leap days
|
|
|
|
dateLeft.setFullYear('1584');
|
|
dateRight.setFullYear('1584'); // Math.abs(diff in full years - diff in calendar years) === 1 if last calendar year is not full
|
|
// If so, result must be decreased by 1 in absolute value
|
|
|
|
var isLastYearNotFull = compareAsc(dateLeft, dateRight) === -sign;
|
|
var result = sign * (difference - isLastYearNotFull); // Prevent negative zero
|
|
|
|
return result === 0 ? 0 : result;
|
|
} |