Yes, the requirement to preserve order predates V8 by years (I believe all the way back to SpiderMonkey, though maybe it was JScript?). Certainly it's long been

Yes, the requirement to preserve order predates V8 by years (I believe all the way back to SpiderMonkey, though maybe it was JScript?). Certainly it's long been the case the web de-facto relies on insertion order being preserved (except V8 found that it didn't really for numeric keys, where there was far more variety between implementations, and Carakan and Chakra followed by similarly dropping order for numeric keys).