Added HammingDistance.js and HammingDistance.test.js in String directory

Author: AbhinavXT

String/HammingDistance.js

@@ -0,0 +1,32 @@
+/**
+ * Hamming Distance: https://en.wikipedia.org/wiki/Hamming_distance
+ *
+ *
+ * Hamming distance is a metric for comparing two binary data strings.
+ *
+ * While comparing two binary strings of equal length, Hamming distance
+ * is the number of bit positions in which the two bits are different.
+ * The Hamming distance between two strings, a and b is denoted as d(a,b)
+ */
+
+/**
+ * @param {string} a
+ * @param {string} b
+ * @return {number}
+ */
+
+export const hammingDistance = (a, b) => {
+  if (a.length !== b.length) {
+    throw new Error('Strings must be of the same length')
+  }
+
+  let distance = 0
+
+  for (let i = 0; i < a.length; i += 1) {
+    if (a[i] !== b[i]) {
+      distance += 1
+    }
+  }
+
+  return distance
+}

String/test/HammingDistance.test.js

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+import { hammingDistance } from '../HammingDistance'
+
+test('should throw an error when trying to compare the strings of different length', () => {
+  const compareStringsOfDifferentLength = () => {
+    hammingDistance('abc', 'abcd')
+  }
+
+  expect(compareStringsOfDifferentLength).toThrowError()
+})
+
+test('should calculate difference between two strings', () => {
+  expect(hammingDistance('a', 'a')).toBe(0)
+})
+
+test('should calculate difference between two strings', () => {
+  expect(hammingDistance('abc', 'add')).toBe(2)
+})
+
+test('should calculate difference between two strings', () => {
+  expect(hammingDistance('1011101', '1001001')).toBe(2)
+})