isWeekend

Checks whether a date falls on a weekend day.

By default, weekend days are Saturday and Sunday (Western convention). Pass a custom weekendDays tuple to adapt to other calendars (e.g. [5, 6] for Friday/Saturday in many Middle-Eastern countries).

Returns false if the input is invalid.

Available since v2.0.0

Import

import { isWeekend } from '@helpers4/date';

Signature

isWeekend(date: DateLike, weekendDays: readonly WeekDay[]): boolean

Parameters

Parameter	Type	Description
date	DateLike	The date to check
weekendDays	readonly WeekDay[]	Override which days count as weekend (default: [0, 6])

Returns

boolean — true if the date’s day-of-week is in weekendDays

Examples

isWeekend

isWeekend('2025-01-18') // => true  (Saturday)
isWeekend('2025-01-19') // => true  (Sunday)
isWeekend('2025-01-20') // => false (Monday)

// Middle-Eastern weekend (Friday + Saturday)
isWeekend('2025-01-17', [WeekDays.Friday, WeekDays.Saturday]) // => true
isWeekend('2025-01-19', [WeekDays.Friday, WeekDays.Saturday]) // => false

Related Types

DateLike

A value that can be converted to a Date.

• Date — used as-is (validated for Invalid Date)
• number — treated as a timestamp (seconds or milliseconds, auto-detected); 0 is treated as invalid and produces null in ensureDate
• string — parsed via new Date(string)
• EpochMilliseconds — any object with a epochMilliseconds property (e.g. Temporal.Instant, Temporal.ZonedDateTime)

// TODO: When the Temporal API reaches Stage 4 and is available without // flags in all major runtimes, consider narrowing the union to the // concrete Temporal types for stricter type-checking.

type DateLike = Date | number | string | EpochMilliseconds

WeekDay

A day-of-week number following the JavaScript Date.getDay() convention: 0 = Sunday, 1 = Monday, … 6 = Saturday.

Prefer using WeekDays named constants for readability: WeekDays.Monday instead of 1.

type WeekDay = (typeof WeekDays)[keyof typeof WeekDays]

EpochMilliseconds

An object that exposes an epoch timestamp in milliseconds.

This structural type is satisfied by Temporal.Instant and Temporal.ZonedDateTime (and any future object that carries the same property), so callers can pass Temporal values without importing them.

interface EpochMilliseconds {
  epochMilliseconds: number;
}

Source

View source on GitHub