@technobuddha/library/src/occurrence-in-month.test.ts

A large library of useful functions

import { day } from './date.ts';
import { occurrenceInMonth } from './occurrence-in-month.ts';

describe('occurrenceInMonth', () => {
  test('should find the occurrences of a day in a month', () => {
    expect(occurrenceInMonth(new Date('1 Aug 2018'), day.sunday, 1)!.toString()).toBe(
      new Date('05 Aug 2018').toString(),
    );
    expect(occurrenceInMonth(new Date('1 Aug 2018'), day.monday, 1)!.toString()).toBe(
      new Date('06 Aug 2018').toString(),
    );
    expect(occurrenceInMonth(new Date('1 Aug 2018'), day.tuesday, 1)!.toString()).toBe(
      new Date('07 Aug 2018').toString(),
    );
    expect(occurrenceInMonth(new Date('1 Aug 2018'), day.wednesday, 1)!.toString()).toBe(
      new Date('01 Aug 2018').toString(),
    );
    expect(occurrenceInMonth(new Date('1 Aug 2018'), day.thursday, 1)!.toString()).toBe(
      new Date('02 Aug 2018').toString(),
    );
    expect(occurrenceInMonth(new Date('1 Aug 2018'), day.friday, 1)!.toString()).toBe(
      new Date('03 Aug 2018').toString(),
    );
    expect(occurrenceInMonth(new Date('1 Aug 2018'), day.saturday, 1)!.toString()).toBe(
      new Date('04 Aug 2018').toString(),
    );
    expect(occurrenceInMonth(new Date('1 Aug 2018'), day.sunday, 2)!.toString()).toBe(
      new Date('12 Aug 2018').toString(),
    );
    expect(occurrenceInMonth(new Date('1 Aug 2018'), day.monday, 2)!.toString()).toBe(
      new Date('13 Aug 2018').toString(),
    );
    expect(occurrenceInMonth(new Date('1 Aug 2018'), day.tuesday, 2)!.toString()).toBe(
      new Date('14 Aug 2018').toString(),
    );
    expect(occurrenceInMonth(new Date('1 Aug 2018'), day.wednesday, 2)!.toString()).toBe(
      new Date('08 Aug 2018').toString(),
    );
    expect(occurrenceInMonth(new Date('1 Aug 2018'), day.thursday, 2)!.toString()).toBe(
      new Date('09 Aug 2018').toString(),
    );
    expect(occurrenceInMonth(new Date('1 Aug 2018'), day.friday, 2)!.toString()).toBe(
      new Date('10 Aug 2018').toString(),
    );
    expect(occurrenceInMonth(new Date('1 Aug 2018'), day.saturday, 2)!.toString()).toBe(
      new Date('11 Aug 2018').toString(),
    );
    expect(occurrenceInMonth(new Date('1 Aug 2018'), day.sunday, 3)!.toString()).toBe(
      new Date('19 Aug 2018').toString(),
    );
    expect(occurrenceInMonth(new Date('1 Aug 2018'), day.monday, 3)!.toString()).toBe(
      new Date('20 Aug 2018').toString(),
    );
    expect(occurrenceInMonth(new Date('1 Aug 2018'), day.tuesday, 3)!.toString()).toBe(
      new Date('21 Aug 2018').toString(),
    );
    expect(occurrenceInMonth(new Date('1 Aug 2018'), day.wednesday, 3)!.toString()).toBe(
      new Date('15 Aug 2018').toString(),
    );
    expect(occurrenceInMonth(new Date('1 Aug 2018'), day.thursday, 3)!.toString()).toBe(
      new Date('16 Aug 2018').toString(),
    );
    expect(occurrenceInMonth(new Date('1 Aug 2018'), day.friday, 3)!.toString()).toBe(
      new Date('17 Aug 2018').toString(),
    );
    expect(occurrenceInMonth(new Date('1 Aug 2018'), day.saturday, 3)!.toString()).toBe(
      new Date('18 Aug 2018').toString(),
    );
    expect(occurrenceInMonth(new Date('1 Aug 2018'), day.sunday, 4)!.toString()).toBe(
      new Date('26 Aug 2018').toString(),
    );
    expect(occurrenceInMonth(new Date('1 Aug 2018'), day.monday, 4)!.toString()).toBe(
      new Date('27 Aug 2018').toString(),
    );
    expect(occurrenceInMonth(new Date('1 Aug 2018'), day.tuesday, 4)!.toString()).toBe(
      new Date('28 Aug 2018').toString(),
    );
    expect(occurrenceInMonth(new Date('1 Aug 2018'), day.wednesday, 4)!.toString()).toBe(
      new Date('22 Aug 2018').toString(),
    );
    expect(occurrenceInMonth(new Date('1 Aug 2018'), day.thursday, 4)!.toString()).toBe(
      new Date('23 Aug 2018').toString(),
    );
    expect(occurrenceInMonth(new Date('1 Aug 2018'), day.friday, 4)!.toString()).toBe(
      new Date('24 Aug 2018').toString(),
    );
    expect(occurrenceInMonth(new Date('1 Aug 2018'), day.saturday, 4)!.toString()).toBe(
      new Date('25 Aug 2018').toString(),
    );
    expect(occurrenceInMonth(new Date('1 Aug 2018'), day.sunday, 5)).toBeNull();
    expect(occurrenceInMonth(new Date('1 Aug 2018'), day.monday, 5)).toBeNull();
    expect(occurrenceInMonth(new Date('1 Aug 2018'), day.tuesday, 5)).toBeNull();
    expect(occurrenceInMonth(new Date('1 Aug 2018'), day.wednesday, 5)!.toString()).toBe(
      new Date('29 Aug 2018').toString(),
    );
    expect(occurrenceInMonth(new Date('1 Aug 2018'), day.thursday, 5)!.toString()).toBe(
      new Date('30 Aug 2018').toString(),
    );
    expect(occurrenceInMonth(new Date('1 Aug 2018'), day.friday, 5)!.toString()).toBe(
      new Date('31 Aug 2018').toString(),
    );
    expect(occurrenceInMonth(new Date('1 Aug 2018'), day.saturday, 5)).toBeNull();
  });

  test('should find the occurrences of a day in a UTC month', () => {
    expect(
      occurrenceInMonth(new Date('31 Jul 2018 22:00 GMT-04:00'), day.sunday, 1, {
        utc: true,
      })!.toString(),
    ).toBe(new Date('05 Aug 2018 UTC').toString());
    expect(
      occurrenceInMonth(new Date('31 Jul 2018 22:00 GMT-04:00'), day.monday, 1, {
        utc: true,
      })!.toString(),
    ).toBe(new Date('06 Aug 2018 UTC').toString());
    expect(
      occurrenceInMonth(new Date('31 Jul 2018 22:00 GMT-04:00'), day.tuesday, 1, {
        utc: true,
      })!.toString(),
    ).toBe(new Date('07 Aug 2018 UTC').toString());
    expect(
      occurrenceInMonth(new Date('31 Jul 2018 22:00 GMT-04:00'), day.wednesday, 1, {
        utc: true,
      })!.toString(),
    ).toBe(new Date('01 Aug 2018 UTC').toString());
    expect(
      occurrenceInMonth(new Date('31 Jul 2018 22:00 GMT-04:00'), day.thursday, 1, {
        utc: true,
      })!.toString(),
    ).toBe(new Date('02 Aug 2018 UTC').toString());
    expect(
      occurrenceInMonth(new Date('31 Jul 2018 22:00 GMT-04:00'), day.friday, 1, {
        utc: true,
      })!.toString(),
    ).toBe(new Date('03 Aug 2018 UTC').toString());
    expect(
      occurrenceInMonth(new Date('31 Jul 2018 22:00 GMT-04:00'), day.saturday, 1, {
        utc: true,
      })!.toString(),
    ).toBe(new Date('04 Aug 2018 UTC').toString());
    expect(
      occurrenceInMonth(new Date('31 Jul 2018 22:00 GMT-04:00'), day.sunday, 2, {
        utc: true,
      })!.toString(),
    ).toBe(new Date('12 Aug 2018 UTC').toString());
    expect(
      occurrenceInMonth(new Date('31 Jul 2018 22:00 GMT-04:00'), day.monday, 2, {
        utc: true,
      })!.toString(),
    ).toBe(new Date('13 Aug 2018 UTC').toString());
    expect(
      occurrenceInMonth(new Date('31 Jul 2018 22:00 GMT-04:00'), day.tuesday, 2, {
        utc: true,
      })!.toString(),
    ).toBe(new Date('14 Aug 2018 UTC').toString());
    expect(
      occurrenceInMonth(new Date('31 Jul 2018 22:00 GMT-04:00'), day.wednesday, 2, {
        utc: true,
      })!.toString(),
    ).toBe(new Date('08 Aug 2018 UTC').toString());
    expect(
      occurrenceInMonth(new Date('31 Jul 2018 22:00 GMT-04:00'), day.thursday, 2, {
        utc: true,
      })!.toString(),
    ).toBe(new Date('09 Aug 2018 UTC').toString());
    expect(
      occurrenceInMonth(new Date('31 Jul 2018 22:00 GMT-04:00'), day.friday, 2, {
        utc: true,
      })!.toString(),
    ).toBe(new Date('10 Aug 2018 UTC').toString());
    expect(
      occurrenceInMonth(new Date('31 Jul 2018 22:00 GMT-04:00'), day.saturday, 2, {
        utc: true,
      })!.toString(),
    ).toBe(new Date('11 Aug 2018 UTC').toString());
    expect(
      occurrenceInMonth(new Date('31 Jul 2018 22:00 GMT-04:00'), day.sunday, 3, {
        utc: true,
      })!.toString(),
    ).toBe(new Date('19 Aug 2018 UTC').toString());
    expect(
      occurrenceInMonth(new Date('31 Jul 2018 22:00 GMT-04:00'), day.monday, 3, {
        utc: true,
      })!.toString(),
    ).toBe(new Date('20 Aug 2018 UTC').toString());
    expect(
      occurrenceInMonth(new Date('31 Jul 2018 22:00 GMT-04:00'), day.tuesday, 3, {
        utc: true,
      })!.toString(),
    ).toBe(new Date('21 Aug 2018 UTC').toString());
    expect(
      occurrenceInMonth(new Date('31 Jul 2018 22:00 GMT-04:00'), day.wednesday, 3, {
        utc: true,
      })!.toString(),
    ).toBe(new Date('15 Aug 2018 UTC').toString());
    expect(
      occurrenceInMonth(new Date('31 Jul 2018 22:00 GMT-04:00'), day.thursday, 3, {
        utc: true,
      })!.toString(),
    ).toBe(new Date('16 Aug 2018 UTC').toString());
    expect(
      occurrenceInMonth(new Date('31 Jul 2018 22:00 GMT-04:00'), day.friday, 3, {
        utc: true,
      })!.toString(),
    ).toBe(new Date('17 Aug 2018 UTC').toString());
    expect(
      occurrenceInMonth(new Date('31 Jul 2018 22:00 GMT-04:00'), day.saturday, 3, {
        utc: true,
      })!.toString(),
    ).toBe(new Date('18 Aug 2018 UTC').toString());
    expect(
      occurrenceInMonth(new Date('31 Jul 2018 22:00 GMT-04:00'), day.sunday, 4, {
        utc: true,
      })!.toString(),
    ).toBe(new Date('26 Aug 2018 UTC').toString());
    expect(
      occurrenceInMonth(new Date('31 Jul 2018 22:00 GMT-04:00'), day.monday, 4, {
        utc: true,
      })!.toString(),
    ).toBe(new Date('27 Aug 2018 UTC').toString());
    expect(
      occurrenceInMonth(new Date('31 Jul 2018 22:00 GMT-04:00'), day.tuesday, 4, {
        utc: true,
      })!.toString(),
    ).toBe(new Date('28 Aug 2018 UTC').toString());
    expect(
      occurrenceInMonth(new Date('31 Jul 2018 22:00 GMT-04:00'), day.wednesday, 4, {
        utc: true,
      })!.toString(),
    ).toBe(new Date('22 Aug 2018 UTC').toString());
    expect(
      occurrenceInMonth(new Date('31 Jul 2018 22:00 GMT-04:00'), day.thursday, 4, {
        utc: true,
      })!.toString(),
    ).toBe(new Date('23 Aug 2018 UTC').toString());
    expect(
      occurrenceInMonth(new Date('31 Jul 2018 22:00 GMT-04:00'), day.friday, 4, {
        utc: true,
      })!.toString(),
    ).toBe(new Date('24 Aug 2018 UTC').toString());
    expect(
      occurrenceInMonth(new Date('31 Jul 2018 22:00 GMT-04:00'), day.saturday, 4, {
        utc: true,
      })!.toString(),
    ).toBe(new Date('25 Aug 2018 UTC').toString());
    expect(
      occurrenceInMonth(new Date('31 Jul 2018 22:00 GMT-04:00'), day.sunday, 5, { utc: true }),
    ).toBeNull();
    expect(
      occurrenceInMonth(new Date('31 Jul 2018 22:00 GMT-04:00'), day.monday, 5, { utc: true }),
    ).toBeNull();
    expect(
      occurrenceInMonth(new Date('31 Jul 2018 22:00 GMT-04:00'), day.tuesday, 5, { utc: true }),
    ).toBeNull();
    expect(
      occurrenceInMonth(new Date('31 Jul 2018 22:00 GMT-04:00'), day.wednesday, 5, {
        utc: true,
      })!.toString(),
    ).toBe(new Date('29 Aug 2018 UTC').toString());
    expect(
      occurrenceInMonth(new Date('31 Jul 2018 22:00 GMT-04:00'), day.thursday, 5, {
        utc: true,
      })!.toString(),
    ).toBe(new Date('30 Aug 2018 UTC').toString());
    expect(
      occurrenceInMonth(new Date('31 Jul 2018 22:00 GMT-04:00'), day.friday, 5, {
        utc: true,
      })!.toString(),
    ).toBe(new Date('31 Aug 2018 UTC').toString());
    expect(
      occurrenceInMonth(new Date('31 Jul 2018 22:00 GMT-04:00'), day.saturday, 5, { utc: true }),
    ).toBeNull();
  });

  test('should check for out of range', () => {
    expect(occurrenceInMonth(new Date('1 Aug 2018'), day.sunday, 0)).toBeNull();
    expect(occurrenceInMonth(new Date('1 Aug 2018'), day.monday, 6)).toBeNull();
  });

  test('should find the last occurrence of a day in a month', () => {
    expect(occurrenceInMonth(new Date('1 Jul 2018'), day.sunday, 'last')!.toString()).toBe(
      new Date('29 Jul 2018').toString(),
    );
    expect(occurrenceInMonth(new Date('1 Jul 2018'), day.monday, 'last')!.toString()).toBe(
      new Date('30 Jul 2018').toString(),
    );
    expect(occurrenceInMonth(new Date('1 Jul 2018'), day.tuesday, 'last')!.toString()).toBe(
      new Date('31 Jul 2018').toString(),
    );
    expect(occurrenceInMonth(new Date('1 Jul 2018'), day.wednesday, 'last')!.toString()).toBe(
      new Date('25 Jul 2018').toString(),
    );
    expect(occurrenceInMonth(new Date('1 Jul 2018'), day.thursday, 'last')!.toString()).toBe(
      new Date('26 Jul 2018').toString(),
    );
    expect(occurrenceInMonth(new Date('1 Jul 2018'), day.friday, 'last')!.toString()).toBe(
      new Date('27 Jul 2018').toString(),
    );
    expect(occurrenceInMonth(new Date('1 Jul 2018'), day.saturday, 'last')!.toString()).toBe(
      new Date('28 Jul 2018').toString(),
    );
  });

  test('should find the last occurrence of a day in a UTC month', () => {
    expect(
      occurrenceInMonth(new Date('30 Jun 2018 22:00 GMT-4:00'), day.sunday, 'last', {
        utc: true,
      })!.toUTCString(),
    ).toBe(new Date('29 Jul 2018 UTC').toUTCString());
    expect(
      occurrenceInMonth(new Date('30 Jun 2018 22:00 GMT-4:00'), day.monday, 'last', {
        utc: true,
      })!.toUTCString(),
    ).toBe(new Date('30 Jul 2018 UTC').toUTCString());
    expect(
      occurrenceInMonth(new Date('30 Jun 2018 22:00 GMT-4:00'), day.tuesday, 'last', {
        utc: true,
      })!.toUTCString(),
    ).toBe(new Date('31 Jul 2018 UTC').toUTCString());
    expect(
      occurrenceInMonth(new Date('30 Jun 2018 22:00 GMT-4:00'), day.wednesday, 'last', {
        utc: true,
      })!.toUTCString(),
    ).toBe(new Date('25 Jul 2018 UTC').toUTCString());
    expect(
      occurrenceInMonth(new Date('30 Jun 2018 22:00 GMT-4:00'), day.thursday, 'last', {
        utc: true,
      })!.toUTCString(),
    ).toBe(new Date('26 Jul 2018 UTC').toUTCString());
    expect(
      occurrenceInMonth(new Date('30 Jun 2018 22:00 GMT-4:00'), day.friday, 'last', {
        utc: true,
      })!.toUTCString(),
    ).toBe(new Date('27 Jul 2018 UTC').toUTCString());
    expect(
      occurrenceInMonth(new Date('30 Jun 2018 22:00 GMT-4:00'), day.saturday, 'last', {
        utc: true,
      })!.toUTCString(),
    ).toBe(new Date('28 Jul 2018 UTC').toUTCString());
  });
});