Today they are not, but they probably should be (or at least I don't see a reason why not).
One potential issue, on the JS side they may try to JSON encode these objects, and then JSON decode them back. The object they get back won't be tied to a dart object or type any more, so its going to act just like a normal js object and get converted to a dart map. Today they will just get an empty object since the fields aren't enumerable, so at least it kind of throws up a red flag that something is not working as expected.
Today they are not, but they probably should be (or at least I don't see a reason why not).
One potential issue, on the JS side they may try to JSON encode these objects, and then JSON decode them back. The object they get back won't be tied to a dart object or type any more, so its going to act just like a normal js object and get converted to a dart map. Today they will just get an empty object since the fields aren't enumerable, so at least it kind of throws up a red flag that something is not working as expected.