index.js
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import getTimezoneOffsetInMilliseconds from '../_lib/getTimezoneOffsetInMilliseconds/index.js';
import startOfISOWeek from '../startOfISOWeek/index.js';
import requiredArgs from '../_lib/requiredArgs/index.js';
var MILLISECONDS_IN_WEEK = 604800000;
/**
* @name differenceInCalendarISOWeeks
* @category ISO Week Helpers
* @summary Get the number of calendar ISO weeks between the given dates.
*
* @description
* Get the number of calendar ISO weeks between the given dates.
*
* ISO week-numbering year: http://en.wikipedia.org/wiki/ISO_week_date
*
* ### 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 calendar ISO weeks
* @throws {TypeError} 2 arguments required
*
* @example
* // How many calendar ISO weeks are between 6 July 2014 and 21 July 2014?
* var result = differenceInCalendarISOWeeks(
* new Date(2014, 6, 21),
* new Date(2014, 6, 6)
* )
* //=> 3
*/
export default function differenceInCalendarISOWeeks(dirtyDateLeft, dirtyDateRight) {
requiredArgs(2, arguments);
var startOfISOWeekLeft = startOfISOWeek(dirtyDateLeft);
var startOfISOWeekRight = startOfISOWeek(dirtyDateRight);
var timestampLeft = startOfISOWeekLeft.getTime() - getTimezoneOffsetInMilliseconds(startOfISOWeekLeft);
var timestampRight = startOfISOWeekRight.getTime() - getTimezoneOffsetInMilliseconds(startOfISOWeekRight); // Round the number of days to the nearest integer
// because the number of milliseconds in a week is not constant
// (e.g. it's different in the week of the daylight saving time clock shift)
return Math.round((timestampLeft - timestampRight) / MILLISECONDS_IN_WEEK);
}