Free Code Camp - Basic Algorithm Scripting - Caesars Cipher

caesars_cipher.js

function rot13(str) { // LBH QVQ VG!
  var decodedStr = "";
  var charShift = 0;
  for (var i = 0, length = str.length; i < length; i++) {
    if ( /[a-m]/i.test(str[i]) ) {
      charShift = 13;
    } else if ( /[n-z]/i.test(str[i] ) ) {
      charShift = -13;
    } else {
      charShift = 0;
    }
    
    if (charShift !== 0) {
      decodedStr += String.fromCharCode(str.charCodeAt(i) + charShift);
    } else {
      decodedStr += str[i];
    }
  }
  
  return decodedStr;
}

// Change the inputs below to test
rot13("SERR PBQR PNZC");