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- import { daysInYear } from './year';
- import { createUTCDate } from '../create/date-from-array';
- // start-of-first-week - start-of-year
- function firstWeekOffset(year, dow, doy) {
- var // first-week day -- which january is always in the first week (4 for iso, 1 for other)
- fwd = 7 + dow - doy,
- // first-week day local weekday -- which local weekday is fwd
- fwdlw = (7 + createUTCDate(year, 0, fwd).getUTCDay() - dow) % 7;
- return -fwdlw + fwd - 1;
- }
- // https://en.wikipedia.org/wiki/ISO_week_date#Calculating_a_date_given_the_year.2C_week_number_and_weekday
- export function dayOfYearFromWeeks(year, week, weekday, dow, doy) {
- var localWeekday = (7 + weekday - dow) % 7,
- weekOffset = firstWeekOffset(year, dow, doy),
- dayOfYear = 1 + 7 * (week - 1) + localWeekday + weekOffset,
- resYear,
- resDayOfYear;
- if (dayOfYear <= 0) {
- resYear = year - 1;
- resDayOfYear = daysInYear(resYear) + dayOfYear;
- } else if (dayOfYear > daysInYear(year)) {
- resYear = year + 1;
- resDayOfYear = dayOfYear - daysInYear(year);
- } else {
- resYear = year;
- resDayOfYear = dayOfYear;
- }
- return {
- year: resYear,
- dayOfYear: resDayOfYear,
- };
- }
- export function weekOfYear(mom, dow, doy) {
- var weekOffset = firstWeekOffset(mom.year(), dow, doy),
- week = Math.floor((mom.dayOfYear() - weekOffset - 1) / 7) + 1,
- resWeek,
- resYear;
- if (week < 1) {
- resYear = mom.year() - 1;
- resWeek = week + weeksInYear(resYear, dow, doy);
- } else if (week > weeksInYear(mom.year(), dow, doy)) {
- resWeek = week - weeksInYear(mom.year(), dow, doy);
- resYear = mom.year() + 1;
- } else {
- resYear = mom.year();
- resWeek = week;
- }
- return {
- week: resWeek,
- year: resYear,
- };
- }
- export function weeksInYear(year, dow, doy) {
- var weekOffset = firstWeekOffset(year, dow, doy),
- weekOffsetNext = firstWeekOffset(year + 1, dow, doy);
- return (daysInYear(year) - weekOffset + weekOffsetNext) / 7;
- }
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