Caesar cipher decoding

[whbob]

Tell us what’s happening:
Describe your issue in detail here.

  **Your code so far**

function rot13(str) {
console.log(str)
var alphaBet = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
console.log(alphaBet)
var shiftedAlpha = "";
var deCoded = " ";
//shifted alphabet
for(let i = 0; i<alphaBet.length; i++)  {
  var offset = (i + 13) % alphaBet.length;
  shiftedAlpha += alphaBet[offset];   }
console.log(shiftedAlpha)
//now step thru the coded string & decode
let result = "";
str = str.toUpperCase();

for(let i = 0; i< str.length; i++)  {
if(!/[A-Z]/.test (str[i]))  {
  result += str[i]; }
let index = shiftedAlpha.indexOf(str[i]);
result += alphaBet[index];  }
console.log(result)

return result;
}

rot13("SERR PBQR PNZC");

SERR PBQR PNZC
ABCDEFGHIJKLMNOPQRSTUVWXYZ
NOPQRSTUVWXYZABCDEFGHIJKLM
FREE undefinedCODE undefinedCAMP

I have decoded the cipher, but I have undefined between the decoded words.
I added an if test to let the spaces pass through. It worked, but the undefined is still there. I have run out of ideas.
I don’t see any characters or non characters that would trigger this.
Any hints would be appreciated.

  **Your browser information:**

User Agent is: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/98.0.4758.109 Safari/537.36

Challenge: Caesars Cipher

Link to the challenge:

freeCodeCamp.org

[peachtin]

Hey! My post is very late and I’m sure you’ve managed to solve this but I’d take another look at your code block where you check for special characters.

It’s a very small thing but you never skip the iteration for when that condition is fulfilled.
If you add continue; or something similar in that block, then you’ll move on to the next iteration. Otherwise you still add undefined from the rest of the for loop.