Re:A div that looks different in every browser
by gsnedders on Tuesday July 10, 2018 @11:03PM
(#17504155)
Nah, the spec has never defined it; it never even mandated insertion order. (I remember a bunch of discussions about this given we, in Carakan, decided to match V8.) https://tc39.github.io/ecma262/#sec-enumerate-object-propert... is the current definition of object enumeration.
But behavior when you deleted an own property that shadowed a property on the proto chain, and what happens when you add such property back.
Also the historic spec mandated integer properties on regular objects were iterated in insertion order as well, but V8 chose not to implement that as doing so broke their "Indexed properties are just an array" semantics. Because of the huge perf impact other browsers had to go down that same path.