45 lines
1.9 KiB
JavaScript
45 lines
1.9 KiB
JavaScript
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import getTimezoneOffsetInMilliseconds from '../_lib/getTimezoneOffsetInMilliseconds/index.js';
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import startOfISOWeek from '../startOfISOWeek/index.js';
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var MILLISECONDS_IN_WEEK = 604800000;
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/**
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* @name differenceInCalendarISOWeeks
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* @category ISO Week Helpers
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* @summary Get the number of calendar ISO weeks between the given dates.
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*
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* @description
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* Get the number of calendar ISO weeks between the given dates.
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*
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* ISO week-numbering year: http://en.wikipedia.org/wiki/ISO_week_date
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*
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* ### v2.0.0 breaking changes:
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*
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* - [Changes that are common for the whole library](https://github.com/date-fns/date-fns/blob/master/docs/upgradeGuide.md#Common-Changes).
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*
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* @param {Date|Number} dateLeft - the later date
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* @param {Date|Number} dateRight - the earlier date
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* @returns {Number} the number of calendar ISO weeks
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* @throws {TypeError} 2 arguments required
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*
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* @example
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* // How many calendar ISO weeks are between 6 July 2014 and 21 July 2014?
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* var result = differenceInCalendarISOWeeks(
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* new Date(2014, 6, 21),
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* new Date(2014, 6, 6)
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* )
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* //=> 3
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*/
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export default function differenceInCalendarISOWeeks(dirtyDateLeft, dirtyDateRight) {
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if (arguments.length < 2) {
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throw new TypeError('2 arguments required, but only ' + arguments.length + ' present');
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}
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var startOfISOWeekLeft = startOfISOWeek(dirtyDateLeft);
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var startOfISOWeekRight = startOfISOWeek(dirtyDateRight);
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var timestampLeft = startOfISOWeekLeft.getTime() - getTimezoneOffsetInMilliseconds(startOfISOWeekLeft);
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var timestampRight = startOfISOWeekRight.getTime() - getTimezoneOffsetInMilliseconds(startOfISOWeekRight); // Round the number of days to the nearest integer
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// because the number of milliseconds in a week is not constant
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// (e.g. it's different in the week of the daylight saving time clock shift)
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return Math.round((timestampLeft - timestampRight) / MILLISECONDS_IN_WEEK);
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}
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