5 files changed, 147 insertions, 0 deletions
diff --git a/date-fns/src/isYesterday/benchmark.js b/date-fns/src/isYesterday/benchmark.js
new file mode 100644
index 0000000..2e333b4
--- /dev/null
+++ b/date-fns/src/isYesterday/benchmark.js
@@ -0,0 +1,19 @@
+// @flow
+/* eslint-env mocha */
+/* global suite, benchmark */
+
+import isYesterday from '.'
+
+suite(
+  'isYesterday',
+  () => {
+    benchmark('date-fns', function() {
+      return isYesterday(this.date)
+    })
+  },
+  {
+    setup: function() {
+      this.date = new Date()
+    }
+  }
+)
diff --git a/date-fns/src/isYesterday/index.d.ts b/date-fns/src/isYesterday/index.d.ts
new file mode 100644
index 0000000..b10c635
--- /dev/null
+++ b/date-fns/src/isYesterday/index.d.ts
@@ -0,0 +1,4 @@
+// This file is generated automatically by `scripts/build/typings.js`. Please, don't change it.
+
+import { isYesterday } from 'date-fns'
+export default isYesterday
diff --git a/date-fns/src/isYesterday/index.js.flow b/date-fns/src/isYesterday/index.js.flow
new file mode 100644
index 0000000..d3f01ee
--- /dev/null
+++ b/date-fns/src/isYesterday/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) => boolean
diff --git a/date-fns/src/isYesterday/index.ts b/date-fns/src/isYesterday/index.ts
new file mode 100644
index 0000000..0946fd9
--- /dev/null
+++ b/date-fns/src/isYesterday/index.ts
@@ -0,0 +1,34 @@
+import isSameDay from '../isSameDay/index'
+import subDays from '../subDays/index'
+import requiredArgs from '../_lib/requiredArgs/index'
+
+/**
+ * @name isYesterday
+ * @category Day Helpers
+ * @summary Is the given date yesterday?
+ * @pure false
+ *
+ * @description
+ * Is the given date yesterday?
+ *
+ * > ⚠️ Please note that this function is not present in the FP submodule as
+ * > it uses `Date.now()` internally hence impure and can't be safely curried.
+ *
+ * ### 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} date - the date to check
+ * @returns {Boolean} the date is yesterday
+ * @throws {TypeError} 1 argument required
+ *
+ * @example
+ * // If today is 6 October 2014, is 5 October 14:00:00 yesterday?
+ * var result = isYesterday(new Date(2014, 9, 5, 14, 0))
+ * //=> true
+ */
+export default function isYesterday(dirtyDate: Date | number): boolean {
+  requiredArgs(1, arguments)
+
+  return isSameDay(dirtyDate, subDays(Date.now(), 1))
+}
diff --git a/date-fns/src/isYesterday/test.ts b/date-fns/src/isYesterday/test.ts
new file mode 100644
index 0000000..4c79b72
--- /dev/null
+++ b/date-fns/src/isYesterday/test.ts
@@ -0,0 +1,38 @@
+// @flow
+/* eslint-env mocha */
+
+import { SinonFakeTimers } from 'sinon'
+import assert from 'assert'
+import sinon from 'sinon'
+import isYesterday from '.'
+
+describe('isYesterday', () => {
+  let clock: SinonFakeTimers
+  beforeEach(() => {
+    clock = sinon.useFakeTimers(new Date(2014, 8 /* Aug */, 25).getTime())
+  })
+
+  afterEach(() => {
+    clock.restore()
+  })
+
+  it('returns true if the given date is yesterday', () => {
+    const result = isYesterday(new Date(2014, 8 /* Sep */, 24))
+    assert(result === true)
+  })
+
+  it('returns false if the given date is not yesterday', () => {
+    const result = isYesterday(new Date(2014, 8 /* Sep */, 25))
+    assert(result === false)
+  })
+
+  it('accepts a timestamp', () => {
+    const result = isYesterday(new Date(2014, 8 /* Sep */, 24).getTime())
+    assert(result === true)
+  })
+
+  it('throws TypeError exception if passed less than 1 argument', () => {
+    // @ts-expect-error
+    assert.throws(isYesterday.bind(null), TypeError)
+  })
+})