Comments on: JavaScript New Features (EcmaScript 5)

By: joseanpg

joseanpg — Sat, 27 Feb 2010 19:21:39 +0000

This was true in april-2009 draft, but in final version (december 1009)

arguments

isn’t Array:

10.6. Arguments Object
…
4. Set the [[Class]] internal property of obj to “Arguments”.
5. Let Object be the standard built-in Object constructor (15.2.2).
6. Set the [[Prototype]] internal property of obj to the standard built-in Object prototype object (15.2.4).

By: Sundev Lohr

Sundev Lohr — Wed, 17 Feb 2010 19:05:33 +0000

It seems like ecma 5 is a backtrack from the stricter ecma 4 standard. I guess we have Microsoft to blame for that one… It’s a shame because if we bit the bullet and added things like namespaces and strict typing, then we’d have some real speed increases. Speed is going to be key, what with everything going mobile and to some degree renouncing flash. Have you tried to run anything vaguely complex in javascript on a phone. You can’t really do that much. I guess things like ‘freeze’ will add some speed by helping with encapsulation, but they could do so much more. Oh well, the web was never one to evolve that quickly.

By: jL

jL — Tue, 19 Jan 2010 16:13:04 +0000

Nice stuff, though part of me simply can’t believe there’s _still_ no analogue for sprintf() in javascript…

By: Animal

Animal — Tue, 19 Jan 2010 13:20:00 +0000

@Konrad: You’ve always been able to call Array methods on an arguments object. Just call it directly from Array’s prototype, but invoke it upon the arguments object using “call” or “apply”:

var secondArgOnwards = Array.prototype.slice.call(arguments, 1);

By: xurfa

xurfa — Fri, 15 Jan 2010 18:28:48 +0000

“Unicode 3.0″? Wow, that’s very up-to-date…

By: Justin Love

Justin Love — Sun, 13 Dec 2009 14:12:37 +0000

Thanks for the list. It looks like some of the toJSON methods got cut?

I didn’t happen across an “ES5-rollup” library, so I started one.

http://bitbucket.org/JustinLove/es5/

By: Mark Caudill

Mark Caudill — Sat, 18 Apr 2009 13:04:09 +0000

Brendan: Thanks for the correction! I did look at the spec but I overlooked 10.5 CreateArgumentsObject #5, I only saw the argument getting the Arguments class.

Alo, harmony looks exciting as well, but the fact that ES5 is already making motions to implementation really make the immediate future promising. I can see a year from now us having a “ES5-rollup” library (in Javascript) that attempts compatibility when using “ES3.” Great things to come no matter what though.

By: Brendan Eich

Brendan Eich — Sat, 18 Apr 2009 05:05:29 +0000

Konrad@5:55pm - ES5 does make arguments have Array.prototype in its prototype chain, a change from ES1-3. So you can say arguments.slice(0,2), e.g., and not the overlong Array.prototype.slice.call(arguments,0,2).

Coming in ES Harmony: rest parameters, as drafted for ES4: function foo(fst, snd, …rest) { /* here rest is a true Array instance */ }. To match, the “spread” operator: given an Array arr, you can spread it out so its elements are passed as positional parameters to a function foo, via foo(…arr). With rest and the spread operator, one can compose new and apply without a hardcoded newApply method, and the need for arguments goes away.

/be

By: Mark Caudill, a ninja in waiting » JavaScript New Features …

Mark Caudill, a ninja in waiting » JavaScript New Features … — Wed, 15 Apr 2009 07:01:40 +0000

[...] Originally posted here: Mark Caudill, a ninja in waiting » JavaScript New Features … [...]

By: JavaScript is getting a facelift.

JavaScript is getting a facelift. — Wed, 15 Apr 2009 00:49:28 +0000

[...] Or more like an upgrade. Mark Cuadill has more to say about it. [...]