FreeCodeCamp: Caesars Cipher

rot13.js

'use strict';

const rot13 = (str) => {
  const decrypted = [...str].map(c => {
    let charCode = c.charCodeAt(0);
    if (charCode >= 65 && charCode < 78) {
      charCode += 13;
    }
    else if (charCode >= 78 && charCode <= 90) {
      charCode -= 13;
    }
    return charCode;
  });
  return String.fromCharCode(...decrypted);
}

console.log(rot13("SERR PBQR PNZC. LBH QVQ VG!"));