Enumeración de Propiedades

> o = { x: 1 }
{ x: 1 }
> b = Object.create(o)
{}
> b.y = 2
2
> b.propertyIsEnumerable('x')
false
> b.propertyIsEnumerable('y')
true
> Object.prototype.propertyIsEnumerable('toString')
false
> a = {x:1, y:2 }
{ x: 1, y: 2 }
> b = Object.create(a)
{}
> b.z = 3
3
> for(i in b) console.log(b[i])
3
1
2
undefined
> for(i in b) console.log(i)
z
x
y
undefined
> b.propertyIsEnumerable("toString")
false