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 王天杨
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import { millisecondsInWeek } from "./constants.mjs";
import { startOfISOWeek } from "./startOfISOWeek.mjs";
import { getTimezoneOffsetInMilliseconds } from "./_lib/getTimezoneOffsetInMilliseconds.mjs";
/**
* @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
*
* @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 calendar ISO weeks
*
* @example
* // How many calendar ISO weeks are between 6 July 2014 and 21 July 2014?
* const result = differenceInCalendarISOWeeks(
* new Date(2014, 6, 21),
* new Date(2014, 6, 6)
* )
* //=> 3
*/
export function differenceInCalendarISOWeeks(dateLeft, dateRight) {
const startOfISOWeekLeft = startOfISOWeek(dateLeft);
const startOfISOWeekRight = startOfISOWeek(dateRight);
const timestampLeft =
+startOfISOWeekLeft - getTimezoneOffsetInMilliseconds(startOfISOWeekLeft);
const timestampRight =
+startOfISOWeekRight - getTimezoneOffsetInMilliseconds(startOfISOWeekRight);
// Round the number of weeks 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) / millisecondsInWeek);
}
// Fallback for modularized imports:
export default differenceInCalendarISOWeeks;
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