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HTML

              
                <!-- Caesars Cipher: Project Description

One of the simplest and most widely known ciphers is a Caesar cipher, also known as a shift cipher. In a shift cipher the meanings of the letters are shifted by some set amount.

A common modern use is the ROT13 cipher, where the values of the letters are shifted by 13 places. Thus A ↔ N, B ↔ O and so on.

Write a function which takes a ROT13 encoded string as input and returns a decoded string.

All letters will be uppercase. Do not transform any non-alphabetic character (i.e. spaces, punctuation), but do pass them on.
-->
              
            
!

CSS

              
                
              
            
!

JS

              
                function rot13(str, shift = 13) {
  const alpha = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
  let code = "";
  [...alpha].forEach((l, i) => (code += alpha[(i + shift) % alpha.length]));
  let decode = "";
  [...str].forEach((letter) =>
    code.indexOf(letter) < 0
      ? (decode += letter)
      : (decode += alpha[code.indexOf(letter)])
  );
  return decode;
}

console.log(rot13("SERR PBQR PNZC"));
console.log(rot13("SERR CVMMN!"));
console.log(rot13("SERR YBIR?"));
console.log(rot13("GUR DHVPX OEBJA SBK WHZCF BIRE GUR YNML QBT."));

              
            
!
999px

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