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

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-properties https://tc39.github.io/ecma262/#sec-enumerate-object-propert... is the current definition of object enumeration.