crypt-keyper.js

class Encoder {
  constructor(key) {
    this.key = key;
    this.position = 0;
  }

  encode(msg) {
    let res = [];
    for(let i = 0; i < msg.length; i++) {
      if(msg[i] == ' ') {
        res.push(' '.charCodeAt(0));
        continue;
      }
      let c = msg.charCodeAt(i);


      c += this.key[this.position];

      this.position++;


      if(this.position > this.key.length - 1) {
        this.position = 0;
      }
      res.push(c);
    }
    return String.fromCharCode.apply(this, res);
  }
}

class Decoder {
  constructor(key) {
    this.key = key;
    this.position = 0;
  }

  decode(msg) {
    let res = [];
    for(let i = 0; i < msg.length; i++) {
      if(msg[i] == ' ') {
        res.push(' '.charCodeAt(0));
        continue;
      }
      let c = msg.charCodeAt(i);

      c -= this.key[this.position];

      this.position++;

      if(this.position > this.key.length - 1) {
        this.position = 0;
      }
      res.push(c);
    }
    return String.fromCharCode.apply(this, res);
  }
}

class Bus {
  constructor() {
    const key = [ 1, 7, 38, 42 ];
    this.encoder = new Encoder(key);
    this.decoder = new Decoder(key);
  }

  send(msg) {
    console.log('position: ' + this.encoder.position);
    console.log('======');

    console.log('original message:');
    console.log(msg);

    console.log('------');

    const res = this.encoder.encode(msg);

    console.log('encoded message:');
    console.log(res);

    console.log('------');
    console.log('decoded message:');
    const nm  = this.decoder.decode(res);
    console.log(nm);
  }
}

const bus = new Bus();
bus.send('hello my name is ehren');

bus.send('another');

bus.send('message');

output.txt

position: 0
======
original message:
hello my name is ehren
------
encoded message:
ilp t bt t lfu
------
decoded message:
hello my name is ehren
position: 2
======
original message:
another
------
encoded message:
p{s
------
decoded message:
another
position: 1
======
original message:
message
------
encoded message:
tth
------
decoded message:
message