Added jest file in tests, added description and normal even number test(divisibility by 2 )

Maths/IsEven.js

@@ -1,4 +1,5 @@
-/* Even Number: https://simple.wikipedia.org/wiki/Even_number
+/*
+ * Even Number: https://simple.wikipedia.org/wiki/Even_number
  *
  * function to check if number is even
  * return true if number is even
@@ -10,10 +11,46 @@
  * @return {boolean}
  */
 
-const isEven = (number) => {
-  return (number & 1) === 0
+/*
+ * Checking if number is even using divisibility by 2
+ *
+ * If number is divisible by 2 i.e remainder = 0, then it is even
+ * therefore, the function will return true
+ *
+ * If number is not divisible by 2 i.e remainder != 0, then it is not even i.e odd
+ * therefore, the function will return false
+ */
+
+export const isEven = (number) => {
+  return number % 2 === 0
 }
 
-// testing
-console.log(isEven(4))
-console.log(isEven(7))
+/*
+ * Checking if number is even using bitwise operator
+ *
+ * Bitwise AND (&) compares the bits of the 32
+ * bit binary representations of the number and
+ * returns a number after comparing each bit:
+ *
+ * 0 & 0 -> 0
+ * 0 & 1 -> 0
+ * 1 & 0 -> 0
+ * 1 & 1 -> 1
+ *
+ * For odd numbers, the last binary bit will be 1
+ * and for even numbers, the last binary bit will
+ * be 0.
+ *
+ * As the number is compared with one, all the
+ * other bits except the last will become 0. The
+ * last bit will be 0 for even numbers and 1 for
+ * odd numbers, which is checked with the use
+ * of the equality operator.
+ *
+ * References:
+ * https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Bitwise_AND
+ */
+
+export const isEvenBitwise = (number) => {
+  return (number & 1) === 0
+}

Maths/test/IsEven.test.js

@@ -0,0 +1,21 @@
+import { isEven, isEvenBitwise } from '../IsEven'
+
+test('should return if the number is even or not', () => {
+  const isEvenNumber = isEven(4)
+  expect(isEvenNumber).toBe(true)
+})
+
+test('should return if the number is even or not', () => {
+  const isEvenNumber = isEven(7)
+  expect(isEvenNumber).toBe(false)
+})
+
+test('should return if the number is even or not', () => {
+  const isEvenNumber = isEvenBitwise(6)
+  expect(isEvenNumber).toBe(true)
+})
+
+test('should return if the number is even or not', () => {
+  const isEvenNumber = isEvenBitwise(3)
+  expect(isEvenNumber).toBe(false)
+})