getDayName

1/**
2 * Returns the name of the weekday for a given date.
3 *
4 * @param date - The date to extract the day name from.
5 * @param locale - Optional locale string (default is 'en-US').
6 * @param format - Optional format: 'long', 'short', or 'narrow' (default is 'long').
7 * @returns The day name in the specified locale and format.
8 */
9export function getDayName(
10  date: Date,
11  locale: string = 'en-US',
12  format: 'long' | 'short' | 'narrow' = 'long'
13): string {
14  return new Intl.DateTimeFormat(locale, { weekday: format }).format(date);
15}

1test('returns full weekday name (default)', () => {
2  const date = new Date('2025-06-27'); // Friday
3  expect(getDayName(date)).toBe('Friday');
4});
5
6test('returns short weekday name', () => {
7  const date = new Date('2025-06-27');
8  expect(getDayName(date, 'en-US', 'short')).toBe('Fri');
9});
10
11test('returns narrow weekday name', () => {
12  const date = new Date('2025-06-27');
13  expect(getDayName(date, 'en-US', 'narrow')).toBe('F');
14});
15
16test('returns weekday name in different locale', () => {
17  const date = new Date('2025-06-27');
18  expect(getDayName(date, 'fr-FR')).toBe('vendredi');
19});