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

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
+}