Comment #1 on issue 1858 by [email protected]: Iteration over frozen object is slow
http://code.google.com/p/v8/issues/detail?id=1858
I'm seeing this too. If it was a minor performance hit, I wouldn't care too much, but it's severe. In when.js (https://github.com/cujojs/when), I see a 10x performance increase when I use a noop function instead Object.freeze() in v8.
I also believe that this happens when Object.defineProperty and Object.defineProperties are used to create properties that are effectively frozen, i.e. writable: false, configurable: false. I don't have a test case for that yet, but based on quick tests using when.js, I'm fairly sure it's the case.
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