Classes and composition

amp.js

// ##### CLASS INHERITANCE:
class GuitarAmp {
  constructor ({ cabinet = 'spruce', distortion = '1', volume = '0' } = {}) {
    Object.assign(this, {
      cabinet, distortion, volume
    });
  }
}

class BassAmp extends GuitarAmp {
  constructor (options = {}) {
    super(options);
    this.lowCut = options.lowCut;
  }
}

class ChannelStrip extends BassAmp {
  constructor (options = {}) {
    super(options);
    this.inputLevel = options.inputLevel;
  }
}

const guitaramp = new GuitarAmp();
const bassamp = new BassAmp();
const channelstrip = new ChannelStrip();

console.log('guitaramp', guitaramp);
console.log('bassamp', bassamp);
console.log('channel', channelstrip);

// ##### COMPOSITION EXAMPLE:
const distortion = { distortion: 1 };
const volume = { volume: 1 };
const cabinet = { cabinet: 'maple' };
const lowCut = { lowCut: 1 };
const inputLevel = { inputLevel: 1 };

const GuitarAmpComp = (options) => {
  return Object.assign({}, distortion, volume, cabinet, options);
};

const BassAmpComp = (options) => {
  return Object.assign({volume: 2}, lowCut, cabinet, options);
};

const ChannelStripComp = (options) => {
  return Object.assign({}, inputLevel, lowCut, volume, options);
};

const guitarampcomp = GuitarAmpComp();
const bassampcomp = BassAmpComp();
const channelstripcomp = ChannelStripComp();

console.log('guitarampcomp', guitarampcomp);
console.log('bassampcomp', bassampcomp);
console.log('channelstripcomp', channelstripcomp);