39 lines
1.3 KiB
JavaScript
39 lines
1.3 KiB
JavaScript
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import { millisecondsInWeek } from "./constants.mjs";
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import { startOfISOWeek } from "./startOfISOWeek.mjs";
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import { startOfISOWeekYear } from "./startOfISOWeekYear.mjs";
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import { toDate } from "./toDate.mjs";
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/**
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* @name getISOWeek
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* @category ISO Week Helpers
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* @summary Get the ISO week of the given date.
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*
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* @description
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* Get the ISO week of the given date.
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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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* @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 date - The given date
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*
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* @returns The ISO week
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*
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* @example
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* // Which week of the ISO-week numbering year is 2 January 2005?
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* const result = getISOWeek(new Date(2005, 0, 2))
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* //=> 53
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*/
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export function getISOWeek(date) {
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const _date = toDate(date);
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const diff = +startOfISOWeek(_date) - +startOfISOWeekYear(_date);
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// Round the number of weeks to the nearest integer because the number of
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// milliseconds in a week 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(diff / millisecondsInWeek) + 1;
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}
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// Fallback for modularized imports:
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export default getISOWeek;
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