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A comment on Why the New V8 Is So Damn Fast. Parent comment

Re:Why the New V8 Is So Damn Fast by gsnedders on Monday July 30, 2018 @07:28PM (#17649159)
The ES spec doesn't require it, but every implementation does insertion order (and insertion order was a deliberate decision by Brendan in the original implementation, IIRC), and the web very much relies on it.

The "new" generation of JS VMs (V8, Chakra, Carakan) all dropped insertion order for array index properties (that is properties whose name is a uint32), but kept it for everything else; that broke about as much as browsers are willing to break, and breaking the general case would be far, far worse.

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Re:Why the New V8 Is So Damn Fast by drb91 on Monday July 30, 2018 @08:19PM (#17649489)
Building a browser sometimes feels like building a language where the only guarantee is the worst features will be used and maintained.

I mean this not as a slight on the ecmascript creators/maintainers but rather as an observation of how difficult the problem is.

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