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index.js
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index.js
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import getTimezoneOffsetInMilliseconds from '../_lib/getTimezoneOffsetInMilliseconds/index.js'
import startOfISOWeek from '../startOfISOWeek/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
*
* @param {Date|String|Number} dateLeft - the later date
* @param {Date|String|Number} dateRight - the earlier date
* @param {Options} [options] - the object with options. See [Options]{@link https://date-fns.org/docs/Options}
* @param {0|1|2} [options.additionalDigits=2] - passed to `toDate`. See [toDate]{@link https://date-fns.org/docs/toDate}
* @returns {Number} the number of calendar ISO weeks
* @throws {TypeError} 2 arguments required
* @throws {RangeError} `options.additionalDigits` must be 0, 1 or 2
*
* @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, dirtyOptions) {
if (arguments.length < 2) {
throw new TypeError('2 arguments required, but only ' + arguments.length + ' present')
}
var startOfISOWeekLeft = startOfISOWeek(dirtyDateLeft, dirtyOptions)
var startOfISOWeekRight = startOfISOWeek(dirtyDateRight, dirtyOptions)
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)
}