adding previousDay and its variations

src/index.js

@@ -175,6 +175,14 @@ export { default as nextWednesday } from './nextWednesday/index'
 export { default as parse } from './parse/index'
 export { default as parseISO } from './parseISO/index'
 export { default as parseJSON } from './parseJSON/index'
+export { default as previousDay } from './previousDay/index'
+export { default as previousMonday } from './previousMonday/index'
+export { default as previousTuesday } from './previousTuesday/index'
+export { default as previousWednesday } from './previousWednesday/index'
+export { default as previousThursday } from './previousThursday/index'
+export { default as previousFriday } from './previousFriday/index'
+export { default as previousSaturday } from './previousSaturday/index'
+export { default as previousSunday } from './previousSunday/index'
 export { default as quartersToMonths } from './quartersToMonths/index'
 export { default as quartersToYears } from './quartersToYears/index'
 export { default as roundToNearestMinutes } from './roundToNearestMinutes/index'

src/previousDay/index.ts

@@ -0,0 +1,36 @@
+import requiredArgs from '../_lib/requiredArgs/index'
+import getDay from '../getDay'
+import subDays from '../subDays'
+import { 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 {Day} 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)
+}

src/previousDay/test.ts

@@ -0,0 +1,80 @@
+/* eslint-env mocha */
+
+import assert from 'assert'
+import previousDay from '.'
+
+describe('previousDay', function () {
+  it('returns the previous Monday given various dates after the same', function () {
+    assert.deepStrictEqual(
+      previousDay(new Date(2021, 5 /* Jun */, 18), 1),
+      new Date(2021, 5 /* Jun */, 14)
+    )
+
+    assert.deepStrictEqual(
+      previousDay(new Date(2021, 5 /* Jun */, 17), 1),
+      new Date(2021, 5 /* Jun */, 14)
+    )
+
+    assert.deepStrictEqual(
+      previousDay(new Date(2021, 5 /* Jun */, 14), 1),
+      new Date(2021, 5 /* Jun */, 7)
+    )
+
+    assert.deepStrictEqual(
+      previousDay(new Date(2021, 5 /* Jun */, 9), 1),
+      new Date(2021, 5 /* Jun */, 7)
+    )
+
+    assert.deepStrictEqual(
+      previousDay(new Date(2021, 5 /* Jun */, 8), 1),
+      new Date(2021, 5 /* Jun */, 7)
+    )
+
+    assert.deepStrictEqual(
+      previousDay(new Date(2021, 5 /* Jun */, 7), 1),
+      new Date(2021, 4 /* May */, 31)
+    )
+  })
+
+  it('returns the previous Tuesday given the Saturday after it', function () {
+    assert.deepStrictEqual(
+      previousDay(new Date(2021, 5 /* Jun */, 26), 2),
+      new Date(2021, 5 /* Jun */, 22)
+    )
+  })
+
+  it('returns the previous Wednesday given the Saturday after it', function () {
+    assert.deepStrictEqual(
+      previousDay(new Date(2021, 5 /* Jun */, 26), 3),
+      new Date(2021, 5 /* Jun */, 23)
+    )
+  })
+
+  it('returns the previous Thursday given the Saturday after it', function () {
+    assert.deepStrictEqual(
+      previousDay(new Date(2021, 5 /* Jun */, 26), 4),
+      new Date(2021, 5 /* Jun */, 24)
+    )
+  })
+
+  it('returns the previous Friday given the Saturday after it', function () {
+    assert.deepStrictEqual(
+      previousDay(new Date(2021, 5 /* Jun */, 26), 5),
+      new Date(2021, 5 /* Jun */, 25)
+    )
+  })
+
+  it('returns the previous Saturday given the Saturday after it', function () {
+    assert.deepStrictEqual(
+      previousDay(new Date(2021, 5 /* Jun */, 26), 6),
+      new Date(2021, 5 /* Jun */, 19)
+    )
+  })
+
+  it('returns the previous Sunday given the day is Sunday', function () {
+    assert.deepStrictEqual(
+      previousDay(new Date(2021, 5 /* Jun */, 27), 0),
+      new Date(2021, 5 /* Jun */, 20)
+    )
+  })
+})

src/previousFriday/index.ts

@@ -0,0 +1,25 @@
+import requiredArgs from '../_lib/requiredArgs/index'
+import previousDay from '../previousDay/index'
+import toDate from '../toDate/index'
+
+/**
+ * @name previousFriday
+ * @category Weekday Helpers
+ * @summary When is the previous Friday?
+ *
+ * @description
+ * When is the previous Friday?
+ *
+ * @param {Date | number} date - the date to start counting from
+ * @returns {Date} the previous Friday
+ * @throws {TypeError} 1 argument required
+ *
+ * @example
+ * // When is the previous Friday before Jun, 19, 2021?
+ * const result = previousFriday(new Date(2021, 5, 19))
+ * //=> Fri June 18 2021 00:00:00
+ */
+export default function previousFriday(date: Date | number): Date {
+  requiredArgs(1, arguments)
+  return previousDay(toDate(date), 5)
+}

src/previousFriday/test.ts

@@ -0,0 +1,42 @@
+/* eslint-env mocha */
+
+import assert from 'assert'
+import previousFriday from '.'
+
+describe('previousFriday', function () {
+  it('returns the previous Friday given various dates after the same', function () {
+    assert.deepStrictEqual(
+      previousFriday(new Date(2021, 5 /* Jun */, 5)),
+      new Date(2021, 5 /* Jun */, 4)
+    )
+
+    assert.deepStrictEqual(
+      previousFriday(new Date(2021, 5 /* Jun */, 6)),
+      new Date(2021, 5 /* Jun */, 4)
+    )
+
+    assert.deepStrictEqual(
+      previousFriday(new Date(2021, 5 /* Jun */, 11)),
+      new Date(2021, 5 /* Jun */, 4)
+    )
+
+    assert.deepStrictEqual(
+      previousFriday(new Date(2021, 5 /* Jun */, 14)),
+      new Date(2021, 5 /* Jun */, 11)
+    )
+
+    assert.deepStrictEqual(
+      previousFriday(new Date(2021, 5 /* Jun */, 15)),
+      new Date(2021, 5 /* Jun */, 11)
+    )
+
+    assert.deepStrictEqual(
+      previousFriday(new Date(2021, 5 /* Jun */, 24)),
+      new Date(2021, 5 /* Jun */, 18)
+    )
+  })
+
+  it('returns `Invalid Date` if the given date is invalid', function () {
+    assert(previousFriday(new Date(NaN)) instanceof Date)
+  })
+})

src/previousMonday/index.ts

@@ -0,0 +1,25 @@
+import requiredArgs from '../_lib/requiredArgs/index'
+import previousDay from '../previousDay/index'
+import toDate from '../toDate/index'
+
+/**
+ * @name previousMonday
+ * @category Weekday Helpers
+ * @summary When is the previous Monday?
+ *
+ * @description
+ * When is the previous Monday?
+ *
+ * @param {Date | number} date - the date to start counting from
+ * @returns {Date} the previous Monday
+ * @throws {TypeError} 1 argument required
+ *
+ * @example
+ * // When is the previous Monday before Jun, 18, 2021?
+ * const result = previousMonday(new Date(2021, 5, 18))
+ * //=> Mon June 14 2021 00:00:00
+ */
+export default function previousMonday(date: Date | number): Date {
+  requiredArgs(1, arguments)
+  return previousDay(toDate(date), 1)
+}

src/previousMonday/test.ts

@@ -0,0 +1,42 @@
+/* eslint-env mocha */
+
+import assert from 'assert'
+import previousMonday from '.'
+
+describe('previousMonday', function () {
+  it('returns the previous Monday given various dates after the same', function () {
+    assert.deepStrictEqual(
+      previousMonday(new Date(2021, 5 /* Jun */, 5)),
+      new Date(2021, 4 /* May */, 31)
+    )
+
+    assert.deepStrictEqual(
+      previousMonday(new Date(2021, 5 /* Jun */, 6)),
+      new Date(2021, 4 /* May */, 31)
+    )
+
+    assert.deepStrictEqual(
+      previousMonday(new Date(2021, 5 /* Jun */, 7)),
+      new Date(2021, 4 /* May */, 31)
+    )
+
+    assert.deepStrictEqual(
+      previousMonday(new Date(2021, 5 /* Jun */, 14)),
+      new Date(2021, 5 /* Jun */, 7)
+    )
+
+    assert.deepStrictEqual(
+      previousMonday(new Date(2021, 5 /* Jun */, 15)),
+      new Date(2021, 5 /* Jun */, 14)
+    )
+
+    assert.deepStrictEqual(
+      previousMonday(new Date(2021, 5 /* Jun */, 16)),
+      new Date(2021, 5 /* Jun */, 14)
+    )
+  })
+
+  it('returns `Invalid Date` if the given date is invalid', function () {
+    assert(previousMonday(new Date(NaN)) instanceof Date)
+  })
+})

src/previousSaturday/index.ts

@@ -0,0 +1,25 @@
+import requiredArgs from '../_lib/requiredArgs/index'
+import previousDay from '../previousDay/index'
+import toDate from '../toDate/index'
+
+/**
+ * @name previousSaturday
+ * @category Weekday Helpers
+ * @summary When is the previous Saturday?
+ *
+ * @description
+ * When is the previous Saturday?
+ *
+ * @param {Date | number} date - the date to start counting from
+ * @returns {Date} the previous Saturday
+ * @throws {TypeError} 1 argument required
+ *
+ * @example
+ * // When is the previous Saturday before Jun, 20, 2021?
+ * const result = previousSaturday(new Date(2021, 5, 20))
+ * //=> Fri June 19 2021 00:00:00
+ */
+export default function previousSaturday(date: Date | number): Date {
+  requiredArgs(1, arguments)
+  return previousDay(toDate(date), 6)
+}

src/previousSaturday/test.ts

@@ -0,0 +1,42 @@
+/* eslint-env mocha */
+
+import assert from 'assert'
+import previousSaturday from '.'
+
+describe('previousSaturday', function () {
+  it('returns the previous Saturday given various dates after the same', function () {
+    assert.deepStrictEqual(
+      previousSaturday(new Date(2021, 5 /* Jun */, 7)),
+      new Date(2021, 5 /* Jun */, 5)
+    )
+
+    assert.deepStrictEqual(
+      previousSaturday(new Date(2021, 5 /* Jun */, 8)),
+      new Date(2021, 5 /* Jun */, 5)
+    )
+
+    assert.deepStrictEqual(
+      previousSaturday(new Date(2021, 5 /* Jun */, 12)),
+      new Date(2021, 5 /* Jun */, 5)
+    )
+
+    assert.deepStrictEqual(
+      previousSaturday(new Date(2021, 5 /* Jun */, 16)),
+      new Date(2021, 5 /* Jun */, 12)
+    )
+
+    assert.deepStrictEqual(
+      previousSaturday(new Date(2021, 5 /* Jun */, 17)),
+      new Date(2021, 5 /* Jun */, 12)
+    )
+
+    assert.deepStrictEqual(
+      previousSaturday(new Date(2021, 5 /* Jun */, 24)),
+      new Date(2021, 5 /* Jun */, 19)
+    )
+  })
+
+  it('returns `Invalid Date` if the given date is invalid', function () {
+    assert(previousSaturday(new Date(NaN)) instanceof Date)
+  })
+})

src/previousSunday/index.ts

@@ -0,0 +1,25 @@
+import requiredArgs from '../_lib/requiredArgs/index'
+import previousDay from '../previousDay/index'
+import toDate from '../toDate/index'
+
+/**
+ * @name previousSunday
+ * @category Weekday Helpers
+ * @summary When is the previous Sunday?
+ *
+ * @description
+ * When is the previous Sunday?
+ *
+ * @param {Date | number} date - the date to start counting from
+ * @returns {Date} the previous Sunday
+ * @throws {TypeError} 1 argument required
+ *
+ * @example
+ * // When is the previous Sunday before Jun, 21, 2021?
+ * const result = previousSunday(new Date(2021, 5, 21))
+ * //=> Fri June 20 2021 00:00:00
+ */
+export default function previousSunday(date: Date | number): Date {
+  requiredArgs(1, arguments)
+  return previousDay(toDate(date), 0)
+}