var o = {
  x:1
};

var two =  Object.create(o);

console.log("o " + o.x); // => 1
console.log("two " + two.x); // => 1

o.x = 2;

console.log("o " + o.x); // => 2
console.log("two " + two.x); // => 2

two.x = 3;

console.log("o " + o.x); // => 2
console.log("two " + two.x); // => 3