ls_course_210_rot13

rot13.js

// Encrypts a provided string using the Rot13 cipher

function rot13(string) {
  function rotate(char, limit) {
    var rotatedCharCode = char.charCodeAt(0) + 13;
    
    if (rotatedCharCode > limit) {
      rotatedCharCode -= 26;
    }
    
    return String.fromCharCode(rotatedCharCode);
  }
  
  var lowerCaseLimit = 122;
  var upperCaseLimit = 90;
  var result = '';
  
  for (var i = 0, len = string.length; i < len; i++) {
    if (string[i].match(/[A-Z]/)) {
      result += rotate(string[i], upperCaseLimit);
    } else if (string[i].match(/[a-z]/)) {
      result += rotate(string[i], lowerCaseLimit);
    } else {
      result += string[i];
    }
  }
  
  return result;
}

console.log(rot13('Teachers open the door, but you must enter by yourself.'));
// Grnpuref bcra gur qbbe, ohg lbh zhfg ragre ol lbhefrys.

console.log(rot13(rot13('Teachers open the door, but you must enter by yourself.')));
// Teachers open the door, but you must enter by yourself.