Brendan, Bradley and others - there's no need to search for a relatively
uncommon use case for ordered maps indexed by keys - a far more common use case
is enumerated data stored numerically, eg, marital status:
{
2: "Married",
1: "Single",
5: "Divorced"
}
Likewise maps from numeric primary key values to display values for the records.
So this use case comes up just about every time JavaScript is manipulating data
coming from a SQL database - extremely common.
On Mar 12, 2011, at 3:47 PM, Brendan Eich <[email protected]> wrote:
>> 3. Object has a useful behavior (similar to Java LinkedHashMap) instead of a
>> surprising behavior (treating indices specially)
>
> The argument from Java leaves many cold.
Argument from Java??? You wound me, sir! I would never argue from the
viewpoint of such a verbose language and far prefer your JavaScript.
To rephrase my argument so that it does not appear to be rooted in Java: take
any library of collection classes from any language: C, C++, Python, perl,
Ruby, Forth, whatever: do you ever find a collection class that is written to
preserve order of string keys but not numeric keys?
I don't know of one.
So we're looking at standardizing a behavior for Object that no one has ever
felt the need to implement as a reusable component.
I would argue this means we're standardizing a very rare use case.
>> This is aside from the performance
>
> Perhaps these people should rewrite their code,
To be fair we're talking about a pretty tiny rewrite, in many cases a one-line
change. I made the change to JQuery is about 5 lines, with no apparent
functional difference in a medium-size app.
If someone can point out a benchmark involving JQuery where Chrome appears to
win due to dense Arrays, I can try it out, verify a performance difference if
it's real, and submit the patch. After all it applies to current Firefox
regardless of what is decided here.
> but now we are in a perverse game: Chrome and possibly other browsers (I
> haven't tested IE9) optimize their code better than other browsers.
Glad to see the phrase "perverse game" here. I feel that the right behavior
for the language is in danger of being sacrificed for an advantage in synthetic
benchmarks that don't reflect the real-world use cases we should really be
optimizing for.
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