chore: Merge pull request #726 from ahamed/master

✨ add an algorithm for checking a year is a leap year or not.

DIRECTORY.md

@@ -156,6 +156,7 @@
   * [IsDivisible](https://github.com/TheAlgorithms/Javascript/blob/master/Maths/IsDivisible.js)
   * [IsEven](https://github.com/TheAlgorithms/Javascript/blob/master/Maths/IsEven.js)
   * [isOdd](https://github.com/TheAlgorithms/Javascript/blob/master/Maths/isOdd.js)
+  * [LeapYear](https://github.com/TheAlgorithms/Javascript/blob/master/Maths/LeapYear.js)
   * [Mandelbrot](https://github.com/TheAlgorithms/Javascript/blob/master/Maths/Mandelbrot.js)
   * [MatrixExponentiationRecursive](https://github.com/TheAlgorithms/Javascript/blob/master/Maths/MatrixExponentiationRecursive.js)
   * [MatrixMultiplication](https://github.com/TheAlgorithms/Javascript/blob/master/Maths/MatrixMultiplication.js)

Maths/LeapYear.js

@@ -0,0 +1,22 @@
+/**
+ * isLeapYear :: Number -> Boolean
+ *
+ * Check if a year is a leap year or not. A leap year is a year which has 366 days.
+ * For the extra +1 day the February month contains 29 days instead of 28 days.
+ *
+ * The logic behind the leap year is-
+ * 1. If the year is divisible by 400 then it is a leap year.
+ * 2. If it is not divisible by 400 but divisible by 100 then it is not a leap year.
+ * 3. If the year is not divisible by 400 but not divisible by 100 and divisible by 4 then a leap year.
+ * 4. Other cases except the describing ones are not a leap year.
+ *
+ * @param {number} year
+ * @returns {boolean} true if this is a leap year, false otherwise.
+ */
+export const isLeapYear = (year) => {
+  if (year % 400 === 0) return true
+  if (year % 100 === 0) return false
+  if (year % 4 === 0) return true
+
+  return false
+}

Maths/test/LeapYear.test.js

@@ -0,0 +1,22 @@
+import { isLeapYear } from '../LeapYear'
+
+describe('Leap Year', () => {
+  it('Should return true on the year 2000', () => {
+    expect(isLeapYear(2000)).toBe(true)
+  })
+  it('Should return false on the year 2001', () => {
+    expect(isLeapYear(2001)).toBe(false)
+  })
+  it('Should return false on the year 2002', () => {
+    expect(isLeapYear(2002)).toBe(false)
+  })
+  it('Should return false on the year 2003', () => {
+    expect(isLeapYear(2003)).toBe(false)
+  })
+  it('Should return false on the year 2004', () => {
+    expect(isLeapYear(2004)).toBe(true)
+  })
+  it('Should return false on the year 1900', () => {
+    expect(isLeapYear(1900)).toBe(false)
+  })
+})