Kata_js_Vigenere_Cipher.js

// https://www.codewars.com/kata/52d1bd3694d26f8d6e0000d3/train/javascript

function VigenèreCipher(key, abc) {

  this.encode = function (message) {

    let upperCase = message == message.toUpperCase();
    message = message.toLowerCase();

    let result = ''
    for (let i = 0, j = 0; i < message.length; i++) {
      const c = message.charAt(i)

      if(abc.indexOf(c) != -1){
        let sum = abc.indexOf(c) + abc.indexOf(key[j].toLowerCase());
        if(sum > abc.length-1) {
          sum = sum - (abc.length)
        }
        result += abc[sum];
      } else{
        result += c;
      }

      j = ++j % key.length
    }
    return upperCase?result.toUpperCase():result.toLowerCase();
  };

  this.decode = function (message) {
    
    let upperCase = message == message.toUpperCase();
    message = message.toLowerCase();

    let result = ''
    for (let i = 0, j = 0; i < message.length; i++) {
      const c = message.charAt(i);
      console.log(c ,"-", abc.indexOf(c) != -1)
      if(abc.indexOf(c) != -1){
        let sum = abc.indexOf(c) - abc.indexOf(key[j].toLowerCase());
        if(sum < 0) {
          sum = sum + (abc.length)
        }
        result += abc[sum];
      }else{
        result += c;
      }
      console.log("result", result);
      j = ++j % key.length
    }
    return upperCase?result.toUpperCase():result.toLowerCase();
  };

}



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

console.log(c.encode('codewars'), 'rovwsoiv');
console.log(c.encode('CODEWARS'), 'ROVWSOIV');
console.log(c.decode('rovwsoiv'), 'codewars');
console.log(c.decode('ROVWSOIV'), 'CODEWARS');


abc = "アイウエオァィゥェォカキクケコサシスセソタチツッテトナニヌネノハヒフヘホマミムメモヤャユュヨョラリルレロワヲンー";
key = "カタカナ"
c = new VigenèreCipher(key, abc);
console.log("result :",c.decode('javscript'),"javscript");
console.log("result :",c.encode('javscript'),"javscript");