> Awesome! That was our conclusion too. It was late Kit and I missed > trying it in other implementations (instead we dug into spec because > we thought it was odd). It turns out V8 (Chrome, Node.js) has a bug > that will make non-enumerable properties enumerable by assigning a new > value as in my previous snippet :O > > I suspect that this only applies to builtin properties on objects, as I > think JSC has a similar issue.
You are right. V8 doesn't have this problem for object properties created with `Object.defineProperty` and friends. Also right again, JSC does appear to have a similar issue (tested Safari 2.0.0 - WebKit Nightly) > Speaking for JSC (but i wouldn't be surprised if V8 did something similar) > we will delay the creation of the majority of builtin properties until > they're actually used, eg. until you actually access Array.prototype.reduce > we won't reify the property. A side effect of this is that when you simply > assign to the property we skip reification, and so the property attributes > are the same as you would get if you were creating a new property. > A simple test would be to see if > Array.prototype.reduce; > Array.prototype.reduce = ... > Results in the correct behaviour. Though it does avoid the bug in JSC, accessing the property before setting it doesn't affect V8 on built-ins as it will still bug. I have made a simple test file here: http://dl.dropbox.com/u/513327/enum_bug.html Another odd thing is that V8 uses the `Array#push` internally for `Object.defineProperties`. I noticed that if I set `Array.prototype.push = 1;` using `Object.defineProperties(…)` would error complaining about `push` not being a function. - JDD _______________________________________________ es-discuss mailing list [email protected] https://mail.mozilla.org/listinfo/es-discuss
