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index.ts
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index.ts
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import requiredArgs from '../_lib/requiredArgs/index'
import getDay from '../getDay/index'
import subDays from '../subDays/index'
import type { Day } from '../types'
/**
* @name previousDay
* @category Weekday Helpers
* @summary When is the previous day of the week?
*
* @description
* When is the previous day of the week? 0-6 the day of the week, 0 represents Sunday.
*
* @param {Date | number} date - the date to check
* @param {number} day - day of the week
* @returns {Date} - the date is the previous day of week
* @throws {TypeError} - 2 arguments required
*
* @example
* // When is the previous Monday before Mar, 20, 2020?
* const result = previousDay(new Date(2020, 2, 20), 1)
* //=> Mon Mar 16 2020 00:00:00
*
* @example
* // When is the previous Tuesday before Mar, 21, 2020?
* const result = previousDay(new Date(2020, 2, 21), 2)
* //=> Tue Mar 17 2020 00:00:00
*/
export default function previousDay(date: Date | number, day: Day): Date {
requiredArgs(2, arguments)
let delta = getDay(date) - day
if (delta <= 0) delta += 7
return subDays(date, delta)
}