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| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 | 1x 1x 1x 1x 1x 1x 86x 86x 86x 86x 86x 86x 86x 86x 14x 14x 14x 86x 2x 2x 70x 70x 86x 62x 8x 86x | import { addTime } from './add-time.ts';
import { beginningOfMonth } from './beginning-of-month.ts';
import { type DateOptions, type DayOfWeek, daysPerWeek } from './date.ts';
import { daysInMonth } from './days-in-month.ts';
import { modulo } from './modulo.ts';
/**
* Determine the date of an occurrence of a weekday within a month
* @param input - A date within the month in question
* @param dayOfWeek - The day of the week to find the occurrence
* @param occurrence - The occurrence number, or 'last' to find the last occurrence
* @param options - see {@link DateOptions}
* @defaultValue utc false
* @returns A date object corresponding to the occurrence requested, or null if no such date exists in the month
* @group Time
* @category Day
*/
export function occurrenceInMonth(
input: Date,
dayOfWeek: DayOfWeek,
occurrence: number | 'last',
{ utc = false }: DateOptions = {},
): Date | null {
let day = beginningOfMonth(input, { utc });
const jump = modulo(dayOfWeek - (utc ? day.getUTCDay() : day.getDay()), daysPerWeek);
if (occurrence === 'last') {
return addTime(day, {
days: jump + Math.floor((daysInMonth(input, { utc }) - jump - 1) / daysPerWeek) * daysPerWeek,
});
} else if (occurrence < 1 || occurrence > 5) {
return null;
}
day = addTime(day, { days: jump + daysPerWeek * (occurrence - 1) });
return (
utc ? day.getUTCMonth() === input.getUTCMonth() : day.getMonth() === input.getMonth()
) ?
day
: null;
}
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