Renaming files according to naming convention (#158)

Ciphers/CaesarsCipher.js

@@ -0,0 +1,36 @@
+/**
+ * Caesar's Cipher - also known as the ROT13 Cipher is when
+ * a letter is replaced by the one that is 13 spaces away
+ * from it in the alphabet. If the letter is in the first half
+ * of the alphabet we add 13, if it's in the latter half we
+ * subtract 13 from the character code value.
+ */
+
+/**
+ * Decrypt a ROT13 cipher
+ * @param {String} str - string to be decrypted
+ * @return {String} decrypted string
+ */
+function rot13 (str) {
+  const response = []
+  const strLength = str.length
+
+  for (let i = 0; i < strLength; i++) {
+    const char = str.charCodeAt(i)
+
+    if (char < 65 || (char > 90 && char < 97) || char > 122) {
+      response.push(str.charAt(i))
+    } else if ((char > 77 && char <= 90) || (char > 109 && char <= 122)) {
+      response.push(String.fromCharCode(str.charCodeAt(i) - 13))
+    } else {
+      response.push(String.fromCharCode(str.charCodeAt(i) + 13))
+    }
+  }
+  return response.join('')
+}
+
+// Caesars Cipher Example
+const encryptedString = 'Uryyb Jbeyq'
+const decryptedString = rot13(encryptedString)
+
+console.log(decryptedString) // Hello World