var bike = {

  frameSize: '19 inch',

  wheelSize: '26 inch',

  tires: 'standard',

  ready: false,

  prepare: function() {

    this.ready = true;

  }

}

​

var mountainBike = {

  frameSize: '18 inch',

  frontSuspender: '20mm'

}

mountainBike.__proto__ = bike;

​

var roadBike = {

  wheelSize: '29 inch',

  tires: 'road'

};

roadBike.__proto__ = bike;

​

var fatBike = Object.create(mountainBike, {

  wheelSize: {value:'27.5 inch'},

  tires: {value:'fat'}

});

​

mountainBike.prepare();

​

//bike.__proto__ = fatBike;

​

// 1. mountainBike.wheelSize  = 19 inch / 26 inch / 27.5 inch / undefined ?

// 2. roadBike.frameSize = 18 inch / 19 inch / 26 inch / undefined ?

// 3. roadBike.ready = true / false/ undefined;

// 4. fatBike.ready = true / false / undefined

​

var elem = document.querySelector('#output');

elem.innerHTML += 'mountainBike.wheelSize: ' +mountainBike.wheelSize+'<br />';

elem.innerHTML += 'roadBike.frameSize: ' + roadBike.frameSize+'<br />';

​

elem.innerHTML += 'roadBike.ready: ' + roadBike.ready+'<br />';

elem.innerHTML += 'fatBike.ready: ' + fatBike.ready+'<br />';

​