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 王天杨
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import { millisecondsInWeek } from "./constants.mjs";
import { startOfWeek } from "./startOfWeek.mjs";
import { startOfWeekYear } from "./startOfWeekYear.mjs";
import { toDate } from "./toDate.mjs";
/**
* The {@link getWeek} function options.
*/
/**
* @name getWeek
* @category Week Helpers
* @summary Get the local week index of the given date.
*
* @description
* Get the local week index of the given date.
* The exact calculation depends on the values of
* `options.weekStartsOn` (which is the index of the first day of the week)
* and `options.firstWeekContainsDate` (which is the day of January, which is always in
* the first week of the week-numbering year)
*
* Week numbering: https://en.wikipedia.org/wiki/Week#The_ISO_week_date_system
*
* @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 date - The given date
* @param options - An object with options
*
* @returns The week
*
* @example
* // Which week of the local week numbering year is 2 January 2005 with default options?
* const result = getWeek(new Date(2005, 0, 2))
* //=> 2
*
* @example
* // Which week of the local week numbering year is 2 January 2005,
* // if Monday is the first day of the week,
* // and the first week of the year always contains 4 January?
* const result = getWeek(new Date(2005, 0, 2), {
* weekStartsOn: 1,
* firstWeekContainsDate: 4
* })
* //=> 53
*/
export function getWeek(date, options) {
const _date = toDate(date);
const diff = +startOfWeek(_date, options) - +startOfWeekYear(_date, options);
// 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(diff / millisecondsInWeek) + 1;
}
// Fallback for modularized imports:
export default getWeek;
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