5 files changed, 136 insertions, 0 deletions
diff --git a/date-fns/src/isExists/benchmark.js b/date-fns/src/isExists/benchmark.js
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index 0000000..167c979
--- /dev/null
+++ b/date-fns/src/isExists/benchmark.js
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+// @flow
+/* eslint-env mocha */
+/* global suite, benchmark */
+
+import isExists from '.'
+
+suite(
+  'isExisting',
+  function() {
+    benchmark('date-fns', function() {
+      return isExists(this.invalidYear, this.invalidMonth, this.invalidDay)
+    })
+  },
+  {
+    setup: function() {
+      this.invalidYear = 2018
+      this.invalidMonth = 1
+      this.invalidDay = 31
+    }
+  }
+)
diff --git a/date-fns/src/isExists/index.d.ts b/date-fns/src/isExists/index.d.ts
new file mode 100644
index 0000000..af919be
--- /dev/null
+++ b/date-fns/src/isExists/index.d.ts
@@ -0,0 +1,4 @@
+// This file is generated automatically by `scripts/build/typings.js`. Please, don't change it.
+
+import { isExists } from 'date-fns'
+export default isExists
diff --git a/date-fns/src/isExists/index.js.flow b/date-fns/src/isExists/index.js.flow
new file mode 100644
index 0000000..810828e
--- /dev/null
+++ b/date-fns/src/isExists/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: (year: number, month: number, day: number) => boolean
diff --git a/date-fns/src/isExists/index.ts b/date-fns/src/isExists/index.ts
new file mode 100644
index 0000000..a15e60a
--- /dev/null
+++ b/date-fns/src/isExists/index.ts
@@ -0,0 +1,38 @@
+/**
+ * @name isExists
+ * @category Common Helpers
+ * @summary Is the given date exists?
+ *
+ * @description
+ * Checks if the given arguments convert to an existing date.
+ *
+ * @param {Number} year of the date to check
+ * @param {Number} month of the date to check
+ * @param {Number} day of the date to check
+ * @returns {Boolean} the date exists
+ * @throws {TypeError} 3 arguments required
+ *
+ * @example
+ * // For the valid date:
+ * var result = isExists(2018, 0, 31)
+ * //=> true
+ *
+ * @example
+ * // For the invalid date:
+ * var result = isExists(2018, 1, 31)
+ * //=> false
+ */
+export default function isExists(year: number, month: number, day: number): boolean {
+  if (arguments.length < 3) {
+    throw new TypeError(
+      '3 argument required, but only ' + arguments.length + ' present'
+    )
+  }
+
+  const date = new Date(year, month, day)
+  return (
+    date.getFullYear() === year &&
+    date.getMonth() === month &&
+    date.getDate() === day
+  )
+}
diff --git a/date-fns/src/isExists/test.ts b/date-fns/src/isExists/test.ts
new file mode 100644
index 0000000..3df2470
--- /dev/null
+++ b/date-fns/src/isExists/test.ts
@@ -0,0 +1,21 @@
+// @flow
+/* eslint-env mocha */
+
+import assert from 'power-assert'
+import isExists from '.'
+
+describe('isValid', function() {
+  it('returns true if the given date is valid', function() {
+    const result = isExists(2018, 0, 31)
+    assert(result === true)
+  })
+
+  it('returns false if the given date is invalid', function() {
+    const result = isExists(2018, 1 /* Feb */, 31)
+    assert(result === false)
+  })
+
+  it('throws TypeError exception if passed less than 3 arguments', function() {
+    assert.throws(isExists.bind(null), TypeError)
+  })
+})