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Starred by 8 users
Status: Fixed
Closed: Dec 2015
HW: ----
NextAction: ----
OS: ----
Priority: 2
Type: Bug

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getOwnPropertyNames does not return names in the insertion order
Project Member Reported by, Dec 11 2013 Back to list
var o = {};
for (var i = 0; i < 10; i++) {
  o['_' + String.fromCharCode(i)] = i;
Object.getOwnPropertyNames(o).map(function(n) { return o[n]; })


[4, 1, 2, 3, 9, 6, 7, 0, 8, 5]

but the expected result is

[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]

This is because the object is in slow mode due to the non ascii identifiers. The same thing happens if the keys are all ascii but there are too many or we delete a key. In other words in happens to all slow mode object.

This is not a violation of ES5 or ES6 but it might be unexpected
Comment 1 by, Aug 18 2015
Labels: Area-Language Harmony
Owner: ----
Status: Available
This is now a spec violation, per, which requires insertion order.

Also, another test case, from on  issue 4118  (the object is in dictionary mode due to too many keyed stores):

var t = {}; 'abcdefghijklmnopqrst'.split('').forEach(function (letter) { t[letter] = letter; }); Object.getOwnPropertyNames(t);
> ["g", "b", "h", "a", "t", "c", "f", "r", "k", "e", "p", "l", "q", "n", "s", "m", "o", "j", "i", "d"]
Comment 2 by, Nov 16 2015
Status: Assigned
The dictionary backing store already keeps track of the insertion/enumeration indices. JSObject::MigrateSlowToFast shows how to iterate over a dictionary in enumeration order. Dictionary::CollectKeysTo and Dictionary::CopyEnumKeysTo should learn from that example.
Ignore #3. After, I think the way to fix it is to use JSReceiver::GetKeys() from Runtime_GetOwnPropertyNames.
Is `Object.assign` using `hasOwnProperty` internally or should I create a new issue for `Object.assign`'s behavior? Right now calling `Object.assign` on one of the example objects above will change the order of the new object's `Object.keys`:

var t = {}; 'abcdefghijklmnopqrst'.split('').forEach(function (letter) { t[letter] = letter; }); Object.keys(Object.assign({}, t));
> ["g", "b", "h", "a", "t", "c", "f", "r", "k", "e", "p", "l", "q", "n", "s", "m", "o", "j", "i", "d"]

I just want to make sure that this behavior gets resolved as well.
Object.assign does not use `hasOwnProperty` internally, but it does only deal with own property keys, provided the runtime function it relies on isn't broken.
FWIW, on ToT:

Echo:v8 caitp$ out/x64.release/d8 
V8 version 4.9.0 (candidate)
d8> var t = {}; 'abcdefghijklmnopqrst'.split('').forEach(function (letter) { t[letter] = letter; }); Object.keys(Object.assign({}, t));
["a", "b", "c", "d", "e", "f", "g", "h", "i", "j", "k", "l", "m", "n", "o", "p", "q", "r", "s", "t"]
Status: Fixed
Indeed, #4 happened in The test cases mentioned in #1 and #5 work correctly now.
Labels: Priority-2
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