isBusinessDay

Checks whether a date falls on a business day (i.e. not a weekend day).

This is the logical inverse of isWeekend. By default, business days are Monday through Friday. Pass a custom weekendDays to adapt to other calendars.

Note: This helper does not account for public holidays — those are country- and region-specific. Use it in combination with your own holiday list if needed.

Returns false if the input is invalid.

Available since v2.0.0

Import

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

Signature

isBusinessDay(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 is not a weekend day

Examples

isBusinessDay

isBusinessDay('2025-01-20') // => true  (Monday)
isBusinessDay('2025-01-18') // => false (Saturday)

// UAE weekend (Friday + Saturday)
const uaeWeekend = [WeekDays.Friday, WeekDays.Saturday] as const;
isBusinessDay('2025-01-19', uaeWeekend) // => true  (Sunday = workday)
isBusinessDay('2025-01-17', uaeWeekend) // => false (Friday = weekend)

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