Fwiw I'd absolutely love a way to create function objects that inherit from an existing custom object.
On Thu, Jan 10, 2019, 2:13 PM Sultan <[email protected] wrote: > >what're the benefits over a object indexed by numbers `const o = > Object.create(null); o[0] = 12; ...`? > > Better "optimisable" heuristics in a similar vain to `TypedArrays`. Most > engines have perf cliffs with indexed objects after a certain threshold, > > Memory: at some point indexed objects have to grow by some factor(* N of > the current size) until it reaches and exceeds your desired size resulting > in more memory use that you bargained for or at some point the engine could > downgrade it to dictionary-mode for any one reason. > > It is a fickle round to cross when you want predictable throughput > performance, TypedArrays afford this, but they are not generic(support any > value). > > >About the other function proposal (`Function.create`) I don't see any > benefits in day to day use having a function without prototype > > Both the Array.create and Function.create are not meant as day-to-day > data-structures. > They are meant as low-level building blocks for abstraction that might be > used on a day-to-day, abstractions that wish to guarantee better > predictable performance. > > >and there'd be no way to get the length or iterate over it if you did. > > You don't need a length property to iterate the array if you own and > manage the data-strucure: > > Exhibit A: > var len = 10 > var arr = Array.create(null, len) > for (var i = 0; i < len; i++) arr[i] > > Exhibit B: (tuple) > > var arr = Array.create(null, 2) > arr[0] = 'a' > arr[1] = 'b' > return a > > In both examples you don't need a length property to access/visit all the > elements in the array given they are both statically known at creation time. > > > On Fri, Jan 11, 2019 at 12:20 AM Jordan Harband <[email protected]> wrote: > >> Sorry if I was unclear; it's *impossible* to have an array without a >> `.length` own property, and there'd be no way to get the length or iterate >> over it if you did. I'm also not clear on why you'd want to store named >> properties on an array, especially if you can't iterate it because it >> doesn't have a length? >> >> On Thu, Jan 10, 2019 at 11:04 AM T.J. Crowder < >> [email protected]> wrote: >> >>> On Thu, Jan 10, 2019 at 1:54 PM Augusto Moura >>> <[email protected]> wrote: >>> > >>> > If you don't want the iterable features neither the own properties, >>> > what're the benefits over a object indexed by numbers `const o = >>> > Object.create(null); o[0] = 12; ...`? >>> >>> Exactly. >>> >>> And re functions, using them as state containers without their usual >>> features seems like a bad idea^H^H^H^H^H^H^H^H edge case best handled >>> by `setPrototypeOf` and `delete`. :-) >>> >>> -- T.J. Crowder >>> _______________________________________________ >>> es-discuss mailing list >>> [email protected] >>> https://mail.mozilla.org/listinfo/es-discuss >>> >> _______________________________________________ >> es-discuss mailing list >> [email protected] >> https://mail.mozilla.org/listinfo/es-discuss >> > _______________________________________________ > es-discuss mailing list > [email protected] > https://mail.mozilla.org/listinfo/es-discuss >
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