VigenèreCipher

chiper.js

function VigenèreCipher(key, abc) {
  var keyLen = key.length,
      abcLen = abc.length - 1,
      abcObj,
      abcToObject;
       
  key = key.split('');
  abc = abc.split('');
  
  abcToObject = function (abc) {
      var obj = {};
      abc.forEach(function (elem, index) {
          obj[elem] = index;
      });
      return obj;
  }
  
  abcObj = abcToObject(abc);
  console.log(abcObj);
    
  /** 
   * Encode part
   */
  this.encode = function (str) {
    var encChars = [];
    for (var i = 0, j = 0; i < str.length; i++) {
      
        if (str[i] in abcObj) {
          
          var keyCode = abcObj[key[j % keyLen]],
              charCode = abcObj[str[i]],
              resCode = keyCode + charCode;
            
          encChars.push(abc[resCode % abcLen - 1]);             
          
//           console.log(key[i % keyLen], charCode, keyCode, resCode % abcLen, abc[resCode]);
          
          j++;
        } else {
          console.log("Not in abc", str[i]);
          encChars.push(str[i]);
        }

    }
    return encChars.join('');
  };
  
  /**
   * Decode part
   */
  this.decode = function (str) {
      
    var deChars = [];
    for (var i = 0, j = 0; i < str.length; i++) {
        
        if (str[i] in abcObj) {
          var keyCode = abcObj[key[j % keyLen]],
              charCode = abcObj[str[i]],
              resCode = charCode - keyCode;
          
          if (resCode < 0) {
              resCode += abcLen + 1;
          }
          
          deChars.push(abc[resCode % abcLen ]);    
          
          j++;
//           console.log(key[i % keyLen], charCode, keyCode, resCode % 25, abc[resCode]);
        } else {
          deChars.push(str[i]);
        }
             
    }
    return deChars.join('');    
  };
}

var abc, key;
abc = "abcdefghijklmnopqrstuvwxyz";
key = "password"
c = new VigenèreCipher(key, abc);

console.log(c.encode('codewars') === 'rovwsoiv'); //rovwsoiv
console.log(c.encode('codewars'));

console.log(c.decode('laxxhsj')); // returns 'waffles')


abc = "abcdefghijklmnopqrstuvwxyz";
key = "pa"
c = new VigenèreCipher(key, abc);
console.log(c.encode('l o'));
// console.log(c.decode('l o'));

// console.log(c.encode('srawedoc') === 'hrsoarff');
// console.log('Last word');
// console.log(c.encode('srasdsadsadsawedoc') === 'hrsoarff');