I really like this - I'm writing up a ".empty" proposal and I'll include this as part of it, thanks!
On Thu, Apr 30, 2015 at 9:52 AM, C. Scott Ananian <[email protected]> wrote: > On Mon, Feb 23, 2015 at 3:31 PM, Mark S. Miller <[email protected]> > wrote: > >> On Mon, Feb 23, 2015 at 11:59 AM, Isiah Meadows <[email protected]> >> wrote: >>> >>> On Feb 23, 2015 6:06 AM, "Andrea Giammarchi" < >>> [email protected]> wrote: >>> >>> > On Sun, Feb 22, 2015 at 11:18 PM, Jordan Harband <[email protected]> >>> wrote: >>> >> [...] >> >>> >> - We'd definitely want `Map.empty` and `Set.empty` assuming >>> `Object.freeze` actually froze them >>> >>> Object.freeze does not freeze them, as far as I know. It might require >>> method overrides. >>> >> Object.freeze does not freeze their state. A proposal for a way to either >> freeze the state of collections, and/or to create frozen snapshots of >> collections, for future ES would be welcome and appreciated. I encourage >> any such effort to pay attention to Clojure and React. >> > > I ran into this today. > > As a strawman proposal: > > > Add "If TestIntegrityLevel(M, "frozen") is true, throw a TypeError > exception" between steps 3 and 4 of 23.1.3.1 (Map.prototype.clear), > 23.1.3.3 (Map.prototype.delete), 23.1.3.9 (Map.prototype.set), 23.2.3.1 > (Set.prototype.add), 23.2.3.2 (Set.prototype.clear), and 23.2.3.4 > (Set.prototype.delete). > > This wouldn't be some fancy all-singing all-dancing collection snapshot, > and would still leave the user responsible for freezing the prototype, etc, > but it would bring Map and Set back into parity with object (that is, > m.get(f) behaves for the most part like o[f]). > > Users would still have to special-case Map/Set when they implement their > own deepFreeze() methods, etc, but this ensures that the internal list is > actually protected. It is (AFAICT) otherwise impossible in ES6 to maintain > object identity when "freezing" an collection. > --scott > > > _______________________________________________ > es-discuss mailing list > [email protected] > https://mail.mozilla.org/listinfo/es-discuss > >
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