caesarCipher.js

/*-----------------------------------------------------------------------------
1.turn every word into another word by the same process.
2.just like a puzzle
3.the map() method need to assigned to a variable.

the reference is by me, oh yah.
-----------------------------------------------------------------------------*/

function caesarCipher(str, num) {
  arr = str.split("");

  var ascII = arr.map(char => {
    return char.charCodeAt();
  });
  console.log(ascII);

  // ASCII: A-Z: 65-90 a-z:97-122

  var transNum = ascII.map( (char) => {
    // lowerCase
    // upperCase, remember the equal sign
    // if the char is not alphabet, then restore it.
    if (char + num > 122) char -= 26;
    else if (char + num > 90 && char >= 65 && char <= 90) char -= 26;
    else if( char < 65) char -= num;
    return (char += num);
  });

  var toOriginAlpha = transNum.map(char => {
    return String.fromCharCode(char);
  });
  return toOriginAlpha.join("")
}

// zoo -> bqq
caesarCipher("Zoo Keeper", 26);