5 files changed, 195 insertions, 0 deletions
diff --git a/date-fns/src/setISOWeekYear/benchmark.js b/date-fns/src/setISOWeekYear/benchmark.js
new file mode 100644
index 0000000..1f93381
--- /dev/null
+++ b/date-fns/src/setISOWeekYear/benchmark.js
@@ -0,0 +1,21 @@
+// @flow
+/* eslint-env mocha */
+/* global suite, benchmark */
+
+import setISOWeekYear from '.'
+import moment from 'moment'
+
+suite('setISOWeekYear', function () {
+  benchmark('date-fns', function () {
+    return setISOWeekYear(this.date, 2008)
+  })
+
+  benchmark('Moment.js', function () {
+    return this.moment.isoWeekYear(2008)
+  })
+}, {
+  setup: function () {
+    this.date = new Date()
+    this.moment = moment()
+  }
+})
diff --git a/date-fns/src/setISOWeekYear/index.d.ts b/date-fns/src/setISOWeekYear/index.d.ts
new file mode 100644
index 0000000..ab8ea95
--- /dev/null
+++ b/date-fns/src/setISOWeekYear/index.d.ts
@@ -0,0 +1,4 @@
+// This file is generated automatically by `scripts/build/typings.js`. Please, don't change it.
+
+import { setISOWeekYear } from 'date-fns'
+export default setISOWeekYear
diff --git a/date-fns/src/setISOWeekYear/index.js.flow b/date-fns/src/setISOWeekYear/index.js.flow
new file mode 100644
index 0000000..43beb65
--- /dev/null
+++ b/date-fns/src/setISOWeekYear/index.js.flow
@@ -0,0 +1,52 @@
+// @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, isoWeekYear: number) => Date
diff --git a/date-fns/src/setISOWeekYear/index.ts b/date-fns/src/setISOWeekYear/index.ts
new file mode 100644
index 0000000..20d0051
--- /dev/null
+++ b/date-fns/src/setISOWeekYear/index.ts
@@ -0,0 +1,49 @@
+import toInteger from '../_lib/toInteger/index'
+import toDate from '../toDate/index'
+import startOfISOWeekYear from '../startOfISOWeekYear/index'
+import differenceInCalendarDays from '../differenceInCalendarDays/index'
+import requiredArgs from '../_lib/requiredArgs/index'
+
+/**
+ * @name setISOWeekYear
+ * @category ISO Week-Numbering Year Helpers
+ * @summary Set the ISO week-numbering year to the given date.
+ *
+ * @description
+ * Set the ISO week-numbering year to the given date,
+ * saving the week number and the weekday number.
+ *
+ * ISO week-numbering year: http://en.wikipedia.org/wiki/ISO_week_date
+ *
+ * ### v2.0.0 breaking changes:
+ *
+ * - [Changes that are common for the whole library](https://github.com/date-fns/date-fns/blob/master/docs/upgradeGuide.md#Common-Changes).
+ *
+ * - The function was renamed from `setISOYear` to `setISOWeekYear`.
+ *   "ISO week year" is short for [ISO week-numbering year](https://en.wikipedia.org/wiki/ISO_week_date).
+ *   This change makes the name consistent with
+ *   locale-dependent week-numbering year helpers, e.g., `setWeekYear`.
+ *
+ * @param {Date|Number} date - the date to be changed
+ * @param {Number} isoWeekYear - the ISO week-numbering year of the new date
+ * @returns {Date} the new date with the ISO week-numbering year set
+ * @throws {TypeError} 2 arguments required
+ *
+ * @example
+ * // Set ISO week-numbering year 2007 to 29 December 2008:
+ * const result = setISOWeekYear(new Date(2008, 11, 29), 2007)
+ * //=> Mon Jan 01 2007 00:00:00
+ */
+export default function setISOWeekYear(dirtyDate: Date | number, dirtyISOWeekYear: number): Date {
+  requiredArgs(2, arguments)
+
+  let date = toDate(dirtyDate)
+  const isoWeekYear = toInteger(dirtyISOWeekYear)
+  const diff = differenceInCalendarDays(date, startOfISOWeekYear(date))
+  const fourthOfJanuary = new Date(0)
+  fourthOfJanuary.setFullYear(isoWeekYear, 0, 4)
+  fourthOfJanuary.setHours(0, 0, 0, 0)
+  date = startOfISOWeekYear(fourthOfJanuary)
+  date.setDate(date.getDate() + diff)
+  return date
+}
diff --git a/date-fns/src/setISOWeekYear/test.ts b/date-fns/src/setISOWeekYear/test.ts
new file mode 100644
index 0000000..c5ea154
--- /dev/null
+++ b/date-fns/src/setISOWeekYear/test.ts
@@ -0,0 +1,69 @@
+// @flow
+/* eslint-env mocha */
+
+import assert from 'power-assert'
+import setISOWeekYear from '.'
+
+describe('setISOWeekYear', function() {
+  it('sets the ISO week-numbering year, saving the ISO week and the day of the week', function() {
+    const result = setISOWeekYear(new Date(2008, 11 /* Dec */, 29), 2007)
+    assert.deepEqual(result, new Date(2007, 0 /* Jan */, 1))
+  })
+
+  it('accepts a timestamp', function() {
+    const result = setISOWeekYear(new Date(2010, 0 /* Jan */, 2).getTime(), 2004)
+    assert.deepEqual(result, new Date(2005, 0 /* Jan */, 1))
+  })
+
+  it('converts a fractional number to an integer', function() {
+    const result = setISOWeekYear(new Date(2008, 11 /* Dec */, 29), 2007.7002)
+    assert.deepEqual(result, new Date(2007, 0 /* Jan */, 1))
+  })
+
+  it('implicitly converts number arguments', function() {
+    // @ts-expect-error
+    const result = setISOWeekYear(new Date(2008, 11 /* Dec */, 29), '2007')
+    assert.deepEqual(result, new Date(2007, 0 /* Jan */, 1))
+  })
+
+  it('does not mutate the original date', function() {
+    const date = new Date(2008, 11 /* Dec */, 29)
+    setISOWeekYear(date, 2000)
+    assert.deepEqual(date, new Date(2008, 11 /* Dec */, 29))
+  })
+
+  it('sets ISO week-numbering years less than 100', function() {
+    const initialDate = new Date(2008, 11 /* Dec */, 29)
+    const expectedResult = new Date(0)
+    expectedResult.setFullYear(7, 0 /* Jan */, 1)
+    expectedResult.setHours(0, 0, 0, 0)
+    const result = setISOWeekYear(initialDate, 7)
+    assert.deepEqual(result, expectedResult)
+  })
+
+  it('handles dates before 100 AD', function() {
+    const initialDate = new Date(0)
+    initialDate.setFullYear(8, 11 /* Dec */, 29)
+    initialDate.setHours(0, 0, 0, 0)
+    const expectedResult = new Date(0)
+    expectedResult.setFullYear(7, 0 /* Jan */, 1)
+    expectedResult.setHours(0, 0, 0, 0)
+    const result = setISOWeekYear(initialDate, 7)
+    assert.deepEqual(result, expectedResult)
+  })
+
+  it('returns `Invalid Date` if the given date is invalid', function() {
+    const result = setISOWeekYear(new Date(NaN), 2007)
+    assert(result instanceof Date && isNaN(result.getTime()))
+  })
+
+  it('returns `Invalid Date` if the given amount is NaN', function() {
+    const result = setISOWeekYear(new Date(2008, 11 /* Dec */, 29), NaN)
+    assert(result instanceof Date && isNaN(result.getTime()))
+  })
+
+  it('throws TypeError exception if passed less than 2 arguments', function() {
+    assert.throws(setISOWeekYear.bind(null), TypeError)
+    assert.throws(setISOWeekYear.bind(null, 1), TypeError)
+  })
+})