@technobuddha/library/getISOWeekOfYear/getISOWeekOfYear.mjs

A large library of useful functions

import { ticksPerWeek, month, day } from '../constants';
import floor from '../floor';
import getBeginningOfWeek from '../getBeginningOfWeek';
import getISOWeeksInYear from '../getISOWeeksInYear';
/**
 * Determine the ISO week number for a given date
 *
 * @param input The date
 * @param __namedParameteres see {@link Options}
 * @default weekOneIncludes Thursday
 * @default firstDayOfWeek Monday
 * @returns the week number (1-53)
 */
export function getISOWeekOfYear(input, { UTC = false, weekOneIncludes = day.thursday, firstDayOfWeek = day.monday } = {}) {
    const bow = getBeginningOfWeek(input, { UTC, firstDayOfWeek });
    const week1 = UTC
        ? getBeginningOfWeek(new Date(Date.UTC(bow.getUTCFullYear(), month.january, weekOneIncludes)), { UTC, firstDayOfWeek })
        : getBeginningOfWeek(new Date(bow.getFullYear(), month.january, weekOneIncludes), { UTC, firstDayOfWeek });
    let week = 1 + floor((bow.getTime() - week1.getTime()) / ticksPerWeek, { tolerance: 0.05 });
    let year = UTC ? bow.getUTCFullYear() : bow.getFullYear();
    const weeks = getISOWeeksInYear(year, { UTC, weekOneIncludes });
    if (week > weeks) {
        year += 1;
        week = 1;
    }
    return { year, week };
}
export default getISOWeekOfYear;