@variantjs/core/src/__tests__/dates/visibleDaysInMonthView.test.ts

VariantJS common functions and utilities

import { WeekDay } from '../../types/Dates';
import visibleDaysInMonthView from '../../dates/visibleDaysInMonthView';

describe('visibleDaysInMonthView', () => {
  it('returns 42 items by adding the days on the next month and the prev month', () => {
    // 2021-10-23
    const date = new Date(2021, 9, 23);

    expect(visibleDaysInMonthView(date, WeekDay.Sunday).length).toBe(42);
    expect(visibleDaysInMonthView(date, WeekDay.Sunday)[0]).toEqual(new Date(2021, 8, 26));
    expect(visibleDaysInMonthView(date, WeekDay.Sunday)[4]).toEqual(new Date(2021, 8, 30));
    expect(visibleDaysInMonthView(date, WeekDay.Sunday)[5]).toEqual(new Date(2021, 9, 1));
    expect(visibleDaysInMonthView(date, WeekDay.Sunday)[35]).toEqual(new Date(2021, 9, 31));
    expect(visibleDaysInMonthView(date, WeekDay.Sunday)[36]).toEqual(new Date(2021, 10, 1));
    expect(visibleDaysInMonthView(date, WeekDay.Sunday)[41]).toEqual(new Date(2021, 10, 6));
  });

  it('uses monday as default start of week', () => {
    // 2021-10-23
    const date = new Date(2021, 9, 23);

    expect(visibleDaysInMonthView(date).length).toBe(42);
    expect(visibleDaysInMonthView(date)[0]).toEqual(new Date(2021, 8, 26));
    expect(visibleDaysInMonthView(date)[41]).toEqual(new Date(2021, 10, 6));
  });

  it('returns 35 items by adding the days on the next month and the prev month using a custom start of week', () => {
    // 2021-10-23
    const date = new Date(2021, 9, 23);

    expect(visibleDaysInMonthView(date, WeekDay.Tuesday).length).toBe(35);
    expect(visibleDaysInMonthView(date, WeekDay.Tuesday)[0]).toEqual(new Date(2021, 8, 28));
    expect(visibleDaysInMonthView(date, WeekDay.Tuesday)[6]).toEqual(new Date(2021, 9, 4));
    expect(visibleDaysInMonthView(date, WeekDay.Tuesday)[34]).toEqual(new Date(2021, 10, 1));
  });

  it('returns 42 items by adding the days on the next month and the prev month using a custom start of week', () => {
    // 2021-10-23
    const date = new Date(2021, 9, 23);

    expect(visibleDaysInMonthView(date, WeekDay.Saturday).length).toBe(42);
    expect(visibleDaysInMonthView(date, WeekDay.Saturday)[0]).toEqual(new Date(2021, 8, 25));
    expect(visibleDaysInMonthView(date, WeekDay.Saturday)[41]).toEqual(new Date(2021, 10, 5));
  });

  it('returns 35 items when month ends on last day of week', () => {
    // 2021-07-23
    const date = new Date(2021, 6, 23);

    expect(visibleDaysInMonthView(date, WeekDay.Sunday).length).toBe(35);
    expect(visibleDaysInMonthView(date, WeekDay.Sunday)[0]).toEqual(new Date(2021, 5, 27));
    expect(visibleDaysInMonthView(date, WeekDay.Sunday)[4]).toEqual(new Date(2021, 6, 1));
    expect(visibleDaysInMonthView(date, WeekDay.Sunday)[34]).toEqual(new Date(2021, 6, 31));
  });

  it('returns 35 items when month start on first day of week', () => {
    // 2020-11-23
    const date = new Date(2020, 10, 23);

    expect(visibleDaysInMonthView(date, WeekDay.Sunday).length).toBe(35);
    expect(visibleDaysInMonthView(date, WeekDay.Sunday)[0]).toEqual(new Date(2020, 10, 1));
    expect(visibleDaysInMonthView(date, WeekDay.Sunday)[29]).toEqual(new Date(2020, 10, 30));
    expect(visibleDaysInMonthView(date, WeekDay.Sunday)[34]).toEqual(new Date(2020, 11, 5));
  });

  it('get four rows for a month with 28 days that start on sunday', () => {
    // 2015-02-15
    const date = new Date(2015, 1, 15);

    expect(visibleDaysInMonthView(date, WeekDay.Sunday).length).toBe(28);
    expect(visibleDaysInMonthView(date, WeekDay.Sunday)[0]).toEqual(new Date(2015, 1, 1));
    expect(visibleDaysInMonthView(date, WeekDay.Sunday)[27]).toEqual(new Date(2015, 1, 28));
  });

  it('get four rows for a month with 28 days and first day matches a custom day of week', () => {
    const date = new Date(2021, 1, 15);

    expect(visibleDaysInMonthView(date, WeekDay.Monday).length).toBe(28);
    expect(visibleDaysInMonthView(date, WeekDay.Monday)[0]).toEqual(new Date(2021, 1, 1));
    expect(visibleDaysInMonthView(date, WeekDay.Monday)[27]).toEqual(new Date(2021, 1, 28));
  });


  it('works with dates before 1970', () => {
    const date = new Date('0010-01-01T00:00:00.000Z');

    expect(visibleDaysInMonthView(date, WeekDay.Monday).length).toBe(35);
  });
});