54 lines
1.9 KiB
JavaScript
54 lines
1.9 KiB
JavaScript
import { millisecondsInDay } from "./constants.mjs";
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import { startOfDay } from "./startOfDay.mjs";
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import { getTimezoneOffsetInMilliseconds } from "./_lib/getTimezoneOffsetInMilliseconds.mjs";
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/**
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* @name differenceInCalendarDays
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* @category Day Helpers
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* @summary Get the number of calendar days between the given dates.
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*
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* @description
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* Get the number of calendar days between the given dates. This means that the times are removed
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* from the dates and then the difference in days is calculated.
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*
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* @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).
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*
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* @param dateLeft - The later date
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* @param dateRight - The earlier date
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*
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* @returns The number of calendar days
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*
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* @example
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* // How many calendar days are between
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* // 2 July 2011 23:00:00 and 2 July 2012 00:00:00?
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* const result = differenceInCalendarDays(
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* new Date(2012, 6, 2, 0, 0),
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* new Date(2011, 6, 2, 23, 0)
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* )
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* //=> 366
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* // How many calendar days are between
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* // 2 July 2011 23:59:00 and 3 July 2011 00:01:00?
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* const result = differenceInCalendarDays(
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* new Date(2011, 6, 3, 0, 1),
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* new Date(2011, 6, 2, 23, 59)
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* )
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* //=> 1
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*/
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export function differenceInCalendarDays(dateLeft, dateRight) {
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const startOfDayLeft = startOfDay(dateLeft);
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const startOfDayRight = startOfDay(dateRight);
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const timestampLeft =
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+startOfDayLeft - getTimezoneOffsetInMilliseconds(startOfDayLeft);
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const timestampRight =
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+startOfDayRight - getTimezoneOffsetInMilliseconds(startOfDayRight);
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// Round the number of days to the nearest integer because the number of
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// milliseconds in a day is not constant (e.g. it's different in the week of
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// the daylight saving time clock shift).
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return Math.round((timestampLeft - timestampRight) / millisecondsInDay);
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}
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// Fallback for modularized imports:
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export default differenceInCalendarDays;
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