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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - Defining non-enumerable, non-numeric property breaks for (key in obj) on enumerable, numeric properties"
href="https://bugs.webkit.org/show_bug.cgi?id=146931">146931</a>
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<th>Summary</th>
<td>Defining non-enumerable, non-numeric property breaks for (key in obj) on enumerable, numeric properties
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<th>Classification</th>
<td>Unclassified
</td>
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<th>Product</th>
<td>WebKit
</td>
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<th>Version</th>
<td>528+ (Nightly build)
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<th>Hardware</th>
<td>All
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<th>OS</th>
<td>All
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<th>Status</th>
<td>NEW
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<th>Severity</th>
<td>Normal
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<th>Priority</th>
<td>P2
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<th>Component</th>
<td>JavaScriptCore
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<th>Assignee</th>
<td>webkit-unassigned@lists.webkit.org
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<th>Reporter</th>
<td>mark.s.dittmer@gmail.com
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<pre>This was originally discovered on arrays, but I have since determined that it breaks objects in general. I'm writing a test inline because I'm not sure whether it should be a JavaScriptCore test or LayoutTest.
Test code:
var obj = { 0: 0, 1: 1, _2: 2 };
Object.defineProperty(obj, '_3', {});
for (var key in obj) console.log(key);
Test output:
0
1
0
1
_2
Testing notes:
- Problem occurs on arrays as well as Objects (given that it occurs on plain-old objects, this is not surprising)
- Problem occurs with Object.defineProperty and Object.defineProperties under the same conditions
- Problem only occurs when the newly define property is both non-numeric and non-enumerable (other property attributes do not appear to influence the outcome)
- The only keys that duplicate themselves are numeric keys (that are enumerable)
- Problem does not occur in return value of Object.keys(obj)</pre>
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