5 files changed, 227 insertions, 0 deletions
diff --git a/date-fns/src/differenceInHours/benchmark.js b/date-fns/src/differenceInHours/benchmark.js
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index 0000000..895a26b
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+++ b/date-fns/src/differenceInHours/benchmark.js
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+// @flow
+/* eslint-env mocha */
+/* global suite, benchmark */
+
+import differenceInHours from '.'
+import moment from 'moment'
+
+suite('differenceInHours', function () {
+  benchmark('date-fns', function () {
+    return differenceInHours(this.dateA, this.dateB)
+  })
+
+  benchmark('Moment.js', function () {
+    return this.momentA.diff(this.momentB, 'hour')
+  })
+}, {
+  setup: function () {
+    this.dateA = new Date()
+    this.momentA = moment()
+    this.dateB = new Date(this.dateA.getTime() + 604800000)
+    this.momentB = this.momentA.clone().add(7, 'days')
+  }
+})
diff --git a/date-fns/src/differenceInHours/index.d.ts b/date-fns/src/differenceInHours/index.d.ts
new file mode 100644
index 0000000..4559ab9
--- /dev/null
+++ b/date-fns/src/differenceInHours/index.d.ts
@@ -0,0 +1,4 @@
+// This file is generated automatically by `scripts/build/typings.js`. Please, don't change it.
+
+import { differenceInHours } from 'date-fns'
+export default differenceInHours
diff --git a/date-fns/src/differenceInHours/index.js.flow b/date-fns/src/differenceInHours/index.js.flow
new file mode 100644
index 0000000..c799819
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+++ b/date-fns/src/differenceInHours/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: (
+  dateLeft: Date | number,
+  dateRight: Date | number
+) => number
diff --git a/date-fns/src/differenceInHours/index.ts b/date-fns/src/differenceInHours/index.ts
new file mode 100644
index 0000000..3c940b1
--- /dev/null
+++ b/date-fns/src/differenceInHours/index.ts
@@ -0,0 +1,38 @@
+import differenceInMilliseconds from '../differenceInMilliseconds/index'
+import requiredArgs from '../_lib/requiredArgs/index'
+
+const MILLISECONDS_IN_HOUR = 3600000
+
+/**
+ * @name differenceInHours
+ * @category Hour Helpers
+ * @summary Get the number of hours between the given dates.
+ *
+ * @description
+ * Get the number of hours between the given dates.
+ *
+ * ### 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).
+ *
+ * @param {Date|Number} dateLeft - the later date
+ * @param {Date|Number} dateRight - the earlier date
+ * @returns {Number} the number of hours
+ * @throws {TypeError} 2 arguments required
+ *
+ * @example
+ * // How many hours are between 2 July 2014 06:50:00 and 2 July 2014 19:00:00?
+ * var result = differenceInHours(
+ *   new Date(2014, 6, 2, 19, 0),
+ *   new Date(2014, 6, 2, 6, 50)
+ * )
+ * //=> 12
+ */
+export default function differenceInHours(dirtyDateLeft: Date | number, dirtyDateRight: Date | number): number {
+  requiredArgs(2, arguments)
+
+  const diff =
+    differenceInMilliseconds(dirtyDateLeft, dirtyDateRight) /
+    MILLISECONDS_IN_HOUR
+  return diff > 0 ? Math.floor(diff) : Math.ceil(diff)
+}
diff --git a/date-fns/src/differenceInHours/test.ts b/date-fns/src/differenceInHours/test.ts
new file mode 100644
index 0000000..303b7fa
--- /dev/null
+++ b/date-fns/src/differenceInHours/test.ts
@@ -0,0 +1,107 @@
+// @flow
+/* eslint-env mocha */
+
+import assert from 'assert'
+import differenceInHours from '.'
+
+describe('differenceInHours', function() {
+  it('returns the number of hours between the given dates', function() {
+    const result = differenceInHours(
+      new Date(2014, 6 /* Jul */, 2, 20, 0),
+      new Date(2014, 6 /* Jul */, 2, 6, 0)
+    )
+    assert(result === 14)
+  })
+
+  it('returns a negative number if the time value of the first date is smaller', function() {
+    const result = differenceInHours(
+      new Date(2014, 6 /* Jul */, 2, 6, 0),
+      new Date(2014, 6 /* Jul */, 2, 20, 0)
+    )
+    assert(result === -14)
+  })
+
+  it('accepts timestamps', function() {
+    const result = differenceInHours(
+      new Date(2014, 8 /* Sep */, 5, 18, 0).getTime(),
+      new Date(2014, 8 /* Sep */, 5, 6, 0).getTime()
+    )
+    assert(result === 12)
+  })
+
+  describe('edge cases', function() {
+    it('the difference is less than an hour, but the given dates are in different calendar hours', function() {
+      const result = differenceInHours(
+        new Date(2014, 8 /* Sep */, 5, 12),
+        new Date(2014, 8 /* Sep */, 5, 11, 59)
+      )
+      assert(result === 0)
+    })
+
+    it('the same for the swapped dates', function() {
+      const result = differenceInHours(
+        new Date(2014, 8 /* Sep */, 5, 11, 59),
+        new Date(2014, 8 /* Sep */, 5, 12)
+      )
+      assert(result === 0)
+    })
+
+    it('the difference is an integral number of hours', function() {
+      const result = differenceInHours(
+        new Date(2014, 8 /* Sep */, 5, 13, 0),
+        new Date(2014, 8 /* Sep */, 5, 12, 0)
+      )
+      assert(result === 1)
+    })
+
+    it('the given dates are the same', function() {
+      const result = differenceInHours(
+        new Date(2014, 8 /* Sep */, 5, 0, 0),
+        new Date(2014, 8 /* Sep */, 5, 0, 0)
+      )
+      assert(result === 0)
+    })
+
+    it('does not return -0 when the given dates are the same', () => {
+      function isNegativeZero(x: number): boolean {
+        return x === 0 && 1 / x < 0
+      }
+
+      const result = differenceInHours(
+        new Date(2014, 8 /* Sep */, 5, 0, 0),
+        new Date(2014, 8 /* Sep */, 5, 0, 0)
+      )
+
+      const resultIsNegative = isNegativeZero(result)
+      assert(resultIsNegative === false)
+    })
+  })
+
+  it('returns NaN if the first date is `Invalid Date`', function() {
+    const result = differenceInHours(
+      new Date(NaN),
+      new Date(2017, 0 /* Jan */, 1)
+    )
+    assert(isNaN(result))
+  })
+
+  it('returns NaN if the second date is `Invalid Date`', function() {
+    const result = differenceInHours(
+      new Date(2017, 0 /* Jan */, 1),
+      new Date(NaN)
+    )
+    assert(isNaN(result))
+  })
+
+  it('returns NaN if the both dates are `Invalid Date`', function() {
+    const result = differenceInHours(new Date(NaN), new Date(NaN))
+    assert(isNaN(result))
+  })
+
+  it('throws TypeError exception if passed less than 2 arguments', function() {
+    //@ts-expect-error
+    assert.throws(differenceInHours.bind(null), TypeError)
+    //@ts-expect-error
+    assert.throws(differenceInHours.bind(null, 1), TypeError)
+  })
+})