4 files changed, 218 insertions, 0 deletions
diff --git a/date-fns/src/addBusinessDays/index.d.ts b/date-fns/src/addBusinessDays/index.d.ts
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+++ b/date-fns/src/addBusinessDays/index.d.ts
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+// This file is generated automatically by `scripts/build/typings.js`. Please, don't change it.
+
+import { addBusinessDays } from 'date-fns'
+export default addBusinessDays
diff --git a/date-fns/src/addBusinessDays/index.js.flow b/date-fns/src/addBusinessDays/index.js.flow
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+// @flow
+// This file is generated automatically by `scripts/build/typings.js`. Please, don't change it.
+
+export type Interval = {
+  start: Date | number,
+  end: Date | number,
+}
+
+export type Locale = {
+  code?: string,
+  formatDistance?: (...args: Array<any>) => any,
+  formatRelative?: (...args: Array<any>) => any,
+  localize?: {
+    ordinalNumber: (...args: Array<any>) => any,
+    era: (...args: Array<any>) => any,
+    quarter: (...args: Array<any>) => any,
+    month: (...args: Array<any>) => any,
+    day: (...args: Array<any>) => any,
+    dayPeriod: (...args: Array<any>) => any,
+  },
+  formatLong?: {
+    date: (...args: Array<any>) => any,
+    time: (...args: Array<any>) => any,
+    dateTime: (...args: Array<any>) => any,
+  },
+  match?: {
+    ordinalNumber: (...args: Array<any>) => any,
+    era: (...args: Array<any>) => any,
+    quarter: (...args: Array<any>) => any,
+    month: (...args: Array<any>) => any,
+    day: (...args: Array<any>) => any,
+    dayPeriod: (...args: Array<any>) => any,
+  },
+  options?: {
+    weekStartsOn?: 0 | 1 | 2 | 3 | 4 | 5 | 6,
+    firstWeekContainsDate?: 1 | 2 | 3 | 4 | 5 | 6 | 7,
+  },
+}
+
+export type Duration = {
+  years?: number,
+  months?: number,
+  weeks?: number,
+  days?: number,
+  hours?: number,
+  minutes?: number,
+  seconds?: number,
+}
+
+export type Day = 0 | 1 | 2 | 3 | 4 | 5 | 6
+
+declare module.exports: (date: Date | number, amount: number) => Date
diff --git a/date-fns/src/addBusinessDays/index.ts b/date-fns/src/addBusinessDays/index.ts
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+++ b/date-fns/src/addBusinessDays/index.ts
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+import isWeekend from '../isWeekend/index'
+import toDate from '../toDate/index'
+import toInteger from '../_lib/toInteger/index'
+import requiredArgs from '../_lib/requiredArgs/index'
+import isSunday from '../isSunday/index'
+import isSaturday from '../isSaturday/index'
+
+/**
+ * @name addBusinessDays
+ * @category Day Helpers
+ * @summary Add the specified number of business days (mon - fri) to the given date.
+ *
+ * @description
+ * Add the specified number of business days (mon - fri) to the given date, ignoring weekends.
+ *
+ * @param {Date|Number} date - the date to be changed
+ * @param {Number} amount - the amount of business days to be added. Positive decimals will be rounded using `Math.floor`, decimals less than zero will be rounded using `Math.ceil`.
+ * @returns {Date} the new date with the business days added
+ * @throws {TypeError} 2 arguments required
+ *
+ * @example
+ * // Add 10 business days to 1 September 2014:
+ * const result = addBusinessDays(new Date(2014, 8, 1), 10)
+ * //=> Mon Sep 15 2014 00:00:00 (skipped weekend days)
+ */
+export default function addBusinessDays(
+  dirtyDate: Date | number,
+  dirtyAmount: number
+): Date {
+  requiredArgs(2, arguments)
+
+  const date = toDate(dirtyDate)
+  const startedOnWeekend = isWeekend(date)
+  const amount = toInteger(dirtyAmount)
+
+  if (isNaN(amount)) return new Date(NaN)
+
+  const hours = date.getHours()
+  const sign = amount < 0 ? -1 : 1
+  const fullWeeks = toInteger(amount / 5)
+
+  date.setDate(date.getDate() + fullWeeks * 7)
+
+  // Get remaining days not part of a full week
+  let restDays = Math.abs(amount % 5)
+
+  // Loops over remaining days
+  while (restDays > 0) {
+    date.setDate(date.getDate() + sign)
+    if (!isWeekend(date)) restDays -= 1
+  }
+
+  // If the date is a weekend day and we reduce a dividable of
+  // 5 from it, we land on a weekend date.
+  // To counter this, we add days accordingly to land on the next business day
+  if (startedOnWeekend && isWeekend(date) && amount !== 0) {
+    // If we're reducing days, we want to add days until we land on a weekday
+    // If we're adding days we want to reduce days until we land on a weekday
+    if (isSaturday(date)) date.setDate(date.getDate() + (sign < 0 ? 2 : -1))
+    if (isSunday(date)) date.setDate(date.getDate() + (sign < 0 ? 1 : -2))
+  }
+
+  // Restore hours to avoid DST lag
+  date.setHours(hours)
+
+  return date
+}
diff --git a/date-fns/src/addBusinessDays/test.ts b/date-fns/src/addBusinessDays/test.ts
new file mode 100644
index 0000000..e23bc11
--- /dev/null
+++ b/date-fns/src/addBusinessDays/test.ts
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+// @flow
+/* eslint-env mocha */
+
+import assert from 'assert'
+import addBusinessDays from '.'
+
+describe('addBusinessDays', function() {
+  it('adds the given number of business days', function() {
+    const result = addBusinessDays(new Date(2014, 8 /* Sep */, 1), 10)
+    assert.deepStrictEqual(result, new Date(2014, 8 /* Sep */, 15))
+  })
+
+  it('handles negative amount', function() {
+    const result = addBusinessDays(new Date(2014, 8 /* Sep */, 15), -10)
+    assert.deepStrictEqual(result, new Date(2014, 8 /* Sep */, 1))
+  })
+
+  it('returns the Monday when 1 day is added on the Friday', () => {
+    assert.deepStrictEqual(
+      addBusinessDays(new Date(2020, 0 /* Jan */, 10), 1), // Friday
+      new Date(2020, 0 /* Jan */, 13) // Monday
+    )
+  })
+
+  it('returns the Monday when 1 day is added on the Satuday', () => {
+    assert.deepStrictEqual(
+      addBusinessDays(new Date(2020, 0 /* Jan */, 11), 1), // Saturday
+      new Date(2020, 0 /* Jan */, 13) // Monday
+    )
+  })
+
+  it('returns the Monday when 1 day is added on the Sunday', () => {
+    assert.deepStrictEqual(
+      addBusinessDays(new Date(2020, 0 /* Jan */, 12), 1), // Sunday
+      new Date(2020, 0 /* Jan */, 13) // Monday
+    )
+  })
+
+  it('can handle a large number of business days', function() {
+    // @ts-ignore
+    if (typeof this.timeout === 'function') {
+      // @ts-ignore
+      this.timeout(500 /* 500 ms test timeout */)
+    }
+
+    const result = addBusinessDays(new Date(2014, 0 /* Jan */, 1), 3387885)
+    assert.deepStrictEqual(result, new Date(15000, 0 /* Jan */, 1))
+  })
+
+  it('accepts a timestamp', function() {
+    const result = addBusinessDays(new Date(2014, 8 /* Sep */, 1).getTime(), 10)
+    assert.deepStrictEqual(result, new Date(2014, 8 /* Sep */, 15))
+  })
+
+  it('converts a fractional number to an integer', function() {
+    const result = addBusinessDays(new Date(2014, 8 /* Sep */, 1), 10.5)
+    assert.deepStrictEqual(result, new Date(2014, 8 /* Sep */, 15))
+  })
+
+  it('implicitly converts number arguments', function() {
+    // @ts-expect-error
+    const result = addBusinessDays(new Date(2014, 8 /* Sep */, 1), '10')
+    assert.deepStrictEqual(result, new Date(2014, 8 /* Sep */, 15))
+  })
+
+  it('does not mutate the original date', function() {
+    const date = new Date(2014, 8 /* Sep */, 1)
+    addBusinessDays(date, 11)
+    assert.deepStrictEqual(date, new Date(2014, 8 /* Sep */, 1))
+  })
+
+  it('returns `Invalid Date` if the given date is invalid', function() {
+    const result = addBusinessDays(new Date(NaN), 10)
+    assert(result instanceof Date && isNaN(result.getTime()))
+  })
+
+  it('returns `Invalid Date` if the given amount is NaN', function() {
+    const result = addBusinessDays(new Date(2014, 8 /* Sep */, 1), NaN)
+    assert(result instanceof Date && isNaN(result.getTime()))
+  })
+
+  it('throws TypeError exception if passed less than 2 arguments', function() {
+    // @ts-expect-error
+    assert.throws(addBusinessDays.bind(null), TypeError)
+    // @ts-expect-error
+    assert.throws(addBusinessDays.bind(null, 1), TypeError)
+  })
+  it('starting from a weekend day should land on a weekday when reducing a divisible by 5', function() {
+    const substractResult = addBusinessDays(new Date(2019, 7, 18), -5)
+    assert.deepStrictEqual(substractResult, new Date(2019, 7, 12))
+
+    const addResult = addBusinessDays(new Date(2019, 7, 18), 5)
+    assert.deepStrictEqual(addResult, new Date(2019, 7, 23))
+  })
+})