previousWeekday

Signature

previousWeekday(value: string, dayOfWeek: number, options?: { inclusive?: boolean; }): string

import { previousWeekday } from "@northguild/gmt/plain/calculate";

Return a PlainDate ISO string for the previous occurrence of dayOfWeek on or before value.

• dayOfWeek uses Temporal’s ISO numbering: 1 (Monday) through 7 (Sunday), consistent with getDayOfWeek/parseDayOfWeekFromDate.
• options.inclusive (default false) controls what happens when value already falls on dayOfWeek: false goes back a full week (matching date-fns), true returns value as-is.
• Returns “” on invalid input. Replaces date-fns’s sixteen previous* functions with one parameterized call: | date-fns | gmt | | ––––––––––– | ——————————— | | previousMonday | previousWeekday(value, 1) | | previousTuesday | previousWeekday(value, 2) | | previousWednesday | previousWeekday(value, 3) | | previousThursday | previousWeekday(value, 4) | | previousFriday | previousWeekday(value, 5) | | previousSaturday | previousWeekday(value, 6) | | previousSunday | previousWeekday(value, 7) | | previousDay(v, n) | previousWeekday(value, n) |

Parameters

Parameter	Type	Description
value	string	ISO PlainDate string
dayOfWeek	number	target ISO day of week (1-7, Monday-Sunday)

Options

options

Option	Type	Default
inclusive?	boolean	—

Returns

ISO PlainDate string for the previous occurrence of dayOfWeek, or “” on invalid input

Examples

previousWeekday("2024-03-15", 5) // "2024-03-08" (2024-03-15 is already a Friday, so it goes back a full week)
previousWeekday("2024-03-15", 5, { inclusive: true }) // "2024-03-15"
previousWeekday("2024-03-13", 5) // "2024-03-08" (Wednesday -> previous Friday)
previousWeekday("invalid", 5) // ""
previousWeekday("2024-03-15", 0) // "" (dayOfWeek out of range)

Source

plain/calculate/previousWeekday.ts