This approach is kind of what I was getting at with my postMessage point: window.onmessage = function (data) { let iterator2 = data.iterator; };
But it was pointed out this was rather un-usable, leading to the current discussion. I still would like to see someone respond to jjb's message though: https://mail.mozilla.org/pipermail/es-discuss/2012-October/025531.html From: es-discuss-boun...@mozilla.org [mailto:es-discuss-boun...@mozilla.org] On Behalf Of David Bruant Sent: Saturday, October 6, 2012 13:47 To: Kevin Smith Cc: es-discuss Subject: Re: Symbols, Protocols, Frames, and Versioning I think there is an idea which hasn't been mentionned yet which would be to let programmers "merge" or "assimilate" cross-frame symbols. Basically, when receiving a symbol from some frame, it'd be possible to say "I assimilate this symbol I received from another frame to my own persistableSymble". I haven't thought about all the cases and details, but the idea behind it is to let users match symbols the way they wish preserving unforgeability. I think it would provide a way to solve both cross-frame and maybe dependency-tree issues. David Le 03/10/2012 19:40, Kevin Smith a écrit : One of the main use cases for symbols is for defining object "protocols" that don't suffer from property name conflicts. The recently discussed `iterator` and `toStringTag` method names fall into this category. The idea is that we can implement the protocol by defining methods using symbols, and thus avoid namespacing considerations. Designing and maintaining a global namespace is, well, no fun. But consider the multiple-global case in which we have scripts running in more than one frame. It seems like protocols should be transferrable across frames. For built-in protocols like `iterator`, this has to work: function f(iterable) { for (x of iterable) { // This must work regardless of which frame `iterable` comes from } } But what about user-defined protocols? Let's say we have a "Persistable" protocol: export var persistName = new Symbol; // unique, not "private" And a function which makes use of this protocol: import persistName from "Persistable.js"; function usePersistable(obj) { if (obj[persistName]) obj[persistName](); } It seems like `usePersistable` should be able to work as expected even if `obj` comes from a different frame (in which "Persistable.js" was separately loaded). Another expression of the same problem occurs with versioning. Suppose that in a fairly complex module dependency graph, "Persistable-0.1.js" and "Persistable-0.2.js" are simultaneously loaded. ("Persistable" is on github and therefore in perpetual version-zero purgatory.) It seems reasonable to expect that objects implementing the protocol defined by "Persistable-0.2.js" should be able to work with functions consuming the "Persistable-0.1.js" protocol. But that is not possible with unique symbols. In summary, I don't think that we can really avoid global namespacing issues using system-generated unique symbols as we currently conceive of them. Built-in protocols like `iterator` are a special "cheating" case, but we need to have an equally consistent story for user-defined protocols. Kevin This body part will be downloaded on demand.
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