Add caesar cipher algorithm.

Author: crypt096

caesar-cipher/index.js

@@ -0,0 +1,16 @@
+const caesarCipher = (str, shift, decrypt = false) => {
+  const s = decrypt ? (26 - shift) % 26 : shift;
+  const n = s > 0 ? s : 26 + (s % 26);
+  return [...str]
+    .map((l, i) => {
+      const c = str.charCodeAt(i);
+      if (c >= 65 && c <= 90)
+        return String.fromCharCode(((c - 65 + n) % 26) + 65);
+      if (c >= 97 && c <= 122)
+        return String.fromCharCode(((c - 97 + n) % 26) + 97);
+      return l;
+    })
+    .join('');
+};
+
+console.log(caesarCipher('aleksandar', -3));