the caesar cypher project

caesar/caesar.js

@@ -1,5 +1,23 @@
-const caesar = function() {
+const caesar = function (clearStr, key) {
+  let strArr = clearStr.split("");
 
-}
+  for (let i = 0; i < strArr.length; i++) {
+    const charCode = strArr[i].charCodeAt();
 
-module.exports = caesar
+    if (
+      (charCode >= 65 && charCode <= 90) ||
+      (charCode >= 97 && charCode <= 122)
+    ) {
+      strArr[i] = String.fromCharCode(
+        mod(charCode + key - codeSet(charCode), 26) + codeSet(charCode)
+      );
+    }
+  }
+  //  return matchArr
+  return strArr.join("");
+};
+
+const codeSet = (code) => (code < 97 ? 65 : 97);
+const mod = (n, m) => ((n % m) + m) % m;
+
+module.exports = caesar;