Le 03/10/2011 22:49, Andrea Giammarchi a écrit :
Dear All,
while I had the opportunity to ask directly to Brendan Eich this
question, I would like to ask you 5 minutes of your precious time to
understand common concerns from the JS community, summarized under my
point of view in this post:
http://webreflection.blogspot.com/2011/10/dear-brendan-here-was-my-question.html
I would like to thank you in advance for your time and all possible
answers/considerations/questions you may come up with.
I have seen the sentence "I got 99 problems and JavaScript syntax ain't
one" on twitter (by @mikeal), reused in Brendan's slide of CapitolJS and
at JSConf.eu.
Plenty of people seem to agree with this and I would like to take one
minute to justify why syntax is important in my opinion.
Currently, I can cite only one IDE that has decent JavaScript support:
WebStorm. And they have a very good completion suggestion engine. I have
seen JavaScript IDEs stopping to analyse when coming across the
(function(){...})(); pattern.
Why aren't there that many good JavaScript IDEs? Because JavaScript is
ridiculously hard to analyse. It is weakly typed, and highly dynamic.
For the last months, I have given myself the challenge to come up with a
program which analyse jQuery and is able to retrieve the API. This is
really hard. Most of the API is added with calls to jQuery.extend.
Basically, a program would have to understand the semantics of
jQuery.extend. But also understand that the output of $('a') has such
prototype object with such properties.
This is doable (since the WebStorm people do it), but very hard.
If people have a syntax operator to perform an extend operation, well,
that makes things infinitely easy to analyse, because it becomes part of
the language.
Another example:
----
var o = Object.create(null);
----
What is the o? If Object.create has not been redefined, it's an object.
But it may be anything if Object.create has been redefined.
Consequently, a JavaScript engine can never optimize this line (or may,
but have to guard that Object.create hasn't been redefined which costs a
little something)
---
var o = null <| {};
---
Here, the semantics of this line is guaranteed by the language since
this is syntax and not a function. Consequently, optimizations can be
performed without risking to be compromised.
Syntax additions make the language easier to analyse (allowing better
tooling) and more stable so easier to optimize. Syntax may not be the
concern of a part of the community, but is of another.
Also, I'd like to mention that I'm pro-syntax addition when it covers
things that would benefit from syntax (an extend operator, object
literal additions...), but i won't feed discussions on syntax which do
not bring anything else than readability, namely shorter function
syntax. I have a preference, but do not care of the exact final syntax.
I also do not really care of what the exact final syntax will be, but I
do care that JavaScript contains more syntax for common patterns,
especially the ones that helps analysis and optimizations.
The JavaScript community is not one voice and doesn't have one unique
set of needs. We use the language for different purposes. Some need
crazy performance for awesome graphics/sound experience. Some need more
stability to build tools (linters, IDE plugins, etc.). At JSconf.eu, Lea
Verou mentionned during her talk that she loved Object.prototype.watch
and that she wishes every browsers had this because it's helpful to
write polyfills. Maybe it is time to restart the discussion on "observe"
[1].
I wrote this paragraph because of the sentence "the only thing truly
needed by this community now" in your (Andrea) post.
"the only thing truly needed" does not exist. Maybe several people,
maybe the majority of people want this. But other want other things and
as long as it's justified, TC39 should address all of them.
David
[1] http://wiki.ecmascript.org/doku.php?id=strawman:observe
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