Question

I have an object p, with an enumerable propery x.

var p = Object.create(Object.prototype, {
  x: {
    value: "frog",
    enumerable: true
  }
});

I create an object, that inherits from p, and overrides property x, with a non-enumerable property

var o = Object.create(p, {
  x: {
    value: "bird",
    enumerable: false
  }
});

What do you think, will the property x be enumerated in a for…in loop of o?

for (var n in o) {
  console.log(n);
}

Well, in Chrome and IE9 it will be enumerated (which is, I think, quite wierd); in FF, it won’t be enumerated.

Which one is the right behaviour?

Here is a complete example: http://jsfiddle.net/hnvsM/3/

Answer 1

This is a known bug in V8. There’s been a bug report on this for quite a while.

Issue 705: Non-enumerable property fails to shadow inherited enumerable property from for-in