Caesars Cipher's awkward null

JavaScript
1

Tell us what’s happening:

This function returns a null instead of “A” Why this is happening and how do i elude that error?

Your code so far

function rot13(str) {
  var map = ['A','B','C','D','E','F','G','H','I','J','K','L','M','N','O','P','Q','R','S','T','U','V','W','X','Y','Z'];
  str = str.split("");
  for (var i = 0; i < str.length; i++) {
    var e = map.indexOf(str[i]);
    if (e > 13) {
      str[i] = map[e-13];
    } else if (e <= 13 && e > 0) {
      str[i] = map[e+13];
    } 
  }
  return str;
}

rot13("SERR PBQR PNZC");

Your browser information:

Your Browser User Agent is: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:60.0) Gecko/20100101 Firefox/60.0.

Link to the challenge:
https://www.freecodecamp.org/challenges/caesars-cipher

2

.map is a prototype… not sure you can use it as a variable?
Array.prototype.map()

3

@marioxp97 Arrays are 0-indexed. ‘A’ is at index 0, but you never convert to it. When the index of the ciphertext is 13, you add 13 to it rarther than subtract. Adding 13 to 13 gives you 26, which is out of the bounds of the array. When you’re on 13 (‘N’) you need to subtract to get to ‘A’.

Also you need to join that array of characters back together at the end.

Note, just for readability/simplicity you can just do something like alphabet = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ' then var e = alphabet.indexOf(str[i]), it doesn’t need to be an array, String has an indexOf method as well

1 Like
5

kewl ty Randell , i’m used to a diff language, and
am learning alot from this site :slight_smile:

7

I highly recommend you avoid using variable names that are names of JavaScript built-in methods. That can get confusing quickly.