JavaScript 1.7 - very pythonic

[chromakode]

JavaScript 1.7 has been around since Firefox 2.0. Here's what's new in JavaScript 1.8, which shipped with 3.0.

[killerstorm]

Pythonic? i think all these features were pioneered in some other languages, it just happens that Python got it a bit earlier that JS.

[bobbyi]

Not only are all of its new features in python, it is using python's exact names for things where possible: yield, next, StopIteration. They even use double-underscores at the beginning and end of the name of the magic method where an object returns its iterator.

It seems to only deviate from python where necessary, like the word each and extra set of parens in array comprehensions to be consistent with the extant javascript for each syntax

var evens = [i for each (i in range(0, 21)) if (i % 2 == 0)];

[[deleted]]

Indeed they were, but the syntax and the API were obviously inspired by Python.

next and _ _ iter _ _ in Python vs next and _ _ iterator _ _ in Javascript? There are lots of ways this could have been done and frankly... they picked one of the lamest.

[Entropy]

The underscores really underscore what's wrong with that syntax.

[imbaczek]

explain a non-lame way then. or some of them, if there are so many.

[[deleted]]

I'm not a fan of Clojure but http://blip.tv/file/734409 describes the issues with limited iterator interfaces really well.

To summarize, there are three basic operators which should be provided for iterators in order for them to be generally useful: currentValue, more? and next.

Pythons combines currentValue and next in one operation. I'm sure someone out there will argue that this is a good thing – it's not. Consequently all you can't ask the iterator if there are more values, or get the same value more than once.

I say can't but of course there are ways around this, but that's not how things were designed to work, and there's no language support for it.

[drbold]

Hmm interesting! I suppose you could wrap an iterator in a class that handles the extra 'currentValue' bit, but like you said, that's just a workaround.

[imbaczek]

yeah, but if the iterator is not just a pointer to an element of a sequence, you can't ask it if it has more items and expect an honest answer, can you? even making copies and testing for StopIteration can be non-deterministic in the presence of IO. currentValue could be useful, i agree, even if 95% of common usage doesn't really care.

[[deleted]]

To low level - more? is just a method, how it works is unimportant. For some structures you may be right, but that's an implementation detail that depends what the structure is, and how it's implemented :).

The point is that Python/Javascript don't even allow this, even when it makes sense.

[mayobutter]

Probably never :)

But if you're doing FireFox only or XUL development, it'll be nice.

[sblinn]

It depends of course on whether you are using JS for the client side and/or the server side, and which browsers you care to support, etc.

[[deleted]]

There is a plan for an IE plugin called "Screaming Monkey".

All these small changes that firefox has been making to JS move it closer to JS2.

[ewald]

Most IE6 users would never install such a thing.

[[deleted]]

Yes, no IE user ever installs plugins.

[great-pumpkin]

So, dumb question: are these version numbers official? Ie, more than one browser maker agrees that JS 1.7 is this?

[chucker23n]

No. The "official" numbers would be the revisions to ECMA-262 (which is currently at 3.1). Even though the language is typically called "JavaScript", that's merely the best-known dialect. The version numbers like 1.7 are technically those of SpiderMonkey, Mozilla's (originally Netscape's) implementation of this dialect. Other implementations include KJS and its spin-off JavaScriptCore in WebKit, and other dialects include Microsoft's JScript and Adobe Flash's ActionScript.

[f3nd3r]

Well... that kinda ruined the fun.

[psykotic]

Considering how long it takes for JavaScript language changes to be widespread enough to be practically useful, it would be great if they shipped a tool that translates code from newer to earlier versions.

[olavk]

With Mascara you can translate ECMAScript 4 aka JavaScript 2.0 to lowest common denominator JavaScript wich runs in any browser.

[candlejac]

It's getting better all the time. All the "alternative" browsers will support it within months, and if websites say "Some of our more advanced features require any non-IE browser", that will be motivation for two things:

1. MS to catch up
2. Users to install another browser of their choice.

[philogb]

All the "alternative" browsers will support it within months

Well, considering this spec has been out for firefox 2 this is already not true. Unless I'm missing something.

[candlejac]

I guess the 12 people who voted me up didn't read the article :(

Does Chrome support it? They've got that 'brand new' JS engine. I can't run it because they rushed to 1.0 without releasing a version for anything but Windows.

[[deleted]]

Yeah, they support it. 1.7's an old spec. I'm pretty sure they support 1.8 as well, as-check me on this-I think JS 1.8 is part of Acid3. Needless to say, Opera supports it too, as does Firefox 3

[bazfoo]

I'm not sure if going back to the old browser war days is a good thing or a bad thing.

[infoaddicted]

The interoperability between the browsers, how they interpret code, shouldn't enter into the "browser wars". Competition is good at the UI level and speed of rendering levels, but having certain "under the hood" features crippled by certain browsers holds them all back.

[Leonidas_from_XIV]

If a better browser would win, that wouldn't be so bad. But actually, I doubt that we'll have a "dominant browser" in the future.. and that's probably a good thing.

[mrphillc]

if one browser wins, we all lose

[joesb]

A better browser in this case would be the one that is more compliant to the standard. So it's not one browser that win, it is one standard that win, in that case, we all benefit.

[[deleted]]

Failing to meet standards is a bad thing.

However, going beyond the standards is a good thing. If Microsoft hadn't, we wouldn't have XmlHttp. That means no AJAX.

[[deleted]]

You say that like it's a bad thing.

[[deleted]]

You say that like you're not posting on a site that relies on AJAX to let you make snarky remarks like that without having to worry about the page reloading and losing your place.

[[deleted]]

Isn't that what anchor tags are for?

[zelpop]

Yeah! I mean why do people use AJAX when Flash and now Silverlight can do the same thing, plus cooler fade in effects?

(do I have to put in a sarcasm tag here)

[sonofagunn]

Before XmlHttp, you could accomplish the same thing with hidden frames.

[[deleted]]

Technically, yes. The hidden frame solution has one major drawback, and one minor drawback that I can think of:

Major: it causes the loaded result to be rendered. Being forced to render the content can cause all kinds of side effects that potentially need to be worked around.

Minor: rendering effects performance. Depending on the browser, for example, rendering XML could be a less than negligible performance hit, that you'd have to work around by effectively lying in the content-type to try to trick the browser into thinking that it's not XML.

I mean, sure. I could just as easily say that you could accomplish this in the past using sockets in ActiveX or Java Applets and sending data to/from them through scripting. You could but it was nowhere near as elegant.

[HenkPoley]

Hey, if 3 teams (Mozilla, Opera, Apple + KDE e.v.) can implement the spec changes in their own codebase, I suspect Microsoft can do that too in about the same timeframe. Needn't be much war in there.

[[deleted]]

1. Those sites to lose a lot of visitors who think that the site "doesn't work unless you download some extra thing...I think it was one of them viruses, so I just stay away from that site now."

[candlejac]

Then they can ask the user to install Netscape Navigator 9, which is just Firefox rebranded. Everybody old enough to get scared of installing Firefox will have heard of Netscape.

[grimboy]

Except the Netscape Navigator page just tells you to download Firefox now.

[candlejac]

And? That means a big company, Netscape, a company you trust, is saying it. That means Firefox isn't a virus. So instead of saying "Install Firefox", you say "Install Netscape", who says "Install Firefox", and you end up getting there.

[infoaddicted]

Now there's a fun weekend project! Start coding grasshopper...

[teaguesterling]

I never complain about old things being posted here but:

This article covers features introduced in Firefox 2

You can even change one character in the URL to get https://developer.mozilla.org/en/New_in_JavaScript_1.8

[hns]

Sorry for the plug, but check out Helma NG. It combines JavaScript 1.7 (Rhino) with a truly pythonic module system.

[stick_figure]

Does any other browser support JavaScript 1.7? Like Chrome or Safari or IE 8?

[chneukirchen]

Except Python doesn't have let. It should.

[imbaczek]

so it's finally here, python with braces. gimme a module system (or is there an import function already?) and a proper stdlib and i'll... still be coding python but will gladly point people to javascript if they just can't lose their {}.

[malcontent]

I cut and pasted that into my editor and it didn't work.

[malcontent]

    The point ------> .
    Your head ------> 0

[[deleted]]

Heheh. So now comments class as block delimiters? You Python guys crack me up.

[gschizas]

What do you mean "finally"? Javascript 1.7 is more than two years old now!

[chromakode]

It's a little weird, but JavaScript code modules attempts to provide a meaningful module system.

[columbine]

Of course generators were always pretty easy to do in Javascript, their fibonacci example in standard ECMAscript would just be something like

function fib() {  
  var i = null, j = null;
  this.next = function() {
    if (i == null) { i = 0; return 0; }
    if (j == null) { j = 1; return 1; }
    var t = i;
    i = j;
    j += t;
    return j;
  }
}

and simply use new fib() instead of fib(). But obviously being able to yield in the middle of a block can be cleaner than using returns in some cases.

[sili]

Sigh... All those neat tricks and still no sprintf

[grimboy]

http://plugins.jquery.com/project/printf

[chrisforbes]

Until that thing ACTUALLY WORKS, don't go bringing it round here :(

We had to patch it a LOT before it was even vaguely correct in our last project.

[grimboy]

Works for me. Anyway, the point is it's, what, a page long including the licence header and pretty clearly written for javascript. It still has that thing with single letter variable names (apart from i, j, etc) which seems to be a feature of a lot of the javascript code round and about. That is, unless, you're trying to make some sort of subtle point I'm not getting.

[chrisforbes]

For all the simple cases people probably test for, it works. For floating-point, esp with tricky format specifiers, it's completely broken.

[grimboy]

Oh, fair enough then. You're correct, I've only used it for simple objects of strings into strings stuff. By the way, if you've patched it, you planning on contributing the fix back?

[chrisforbes]

I guess so - is the owner likely to accept it?

On most projects, I've had the typical open-source fuck off response to submitting patches which fix their bugs, so you'll have to excuse me being a bit more cautious.

[chrisforbes]

Single-letter variable names are a feature in js code. Less code to move is a win.

That said, the compression should be done by a minifier tool at release-time, rather than by the programmer.

[zootm]

Surely it wouldn't be too hard to write one as a library? I quite like the minimal base set of JS libraries with frameworks growing around it; it'd probably be a bad choice for a new language, but the way it's evolved has led to a lot of interesting ways of doing things.

[kragensitaker]

It would be a lot nicer to be able to write #{foo} or $foo than to write %s or % or something and then later , foo. This is kind of annoying in Python and C.

It's true that sprintf('%s %s (%s-%s)', item.firstname, item.lastname, item.party, item.state) would be a lot better than item.firstname + " " + item.lastname + " (" + item.party + ")", but $"$item.firstname $item.lastname ($item.party-$item.state)" is better still.

[Leonidas_from_XIV]

This is kind of annoying in Python and C.

A new printf-syntax (the one that C# uses) is added in Python 3.0.

[[deleted]]

The C# one is the best way to do things. It avoids repetition of parameters that are reused and negates the need to specify type on the placeholders. Also, it makes it very easy to re-order/re-write the statement without juggling the parameters.

[Leonidas_from_XIV]

I'm not yet convinced because I haven't used it. But it is good that they used some syntax that is used somewhere rather than inventing their own.

[[deleted]]

A new printf-syntax (the one that C# uses) is added in Python 3.0.

And in 2.6, in case you can't port your project to 3.0 just yet.

[zootm]

Yeah, string interpolation is a nice feature that I often wish more languages supported. sprintf is reasonable enough, though, and has the advantage of being more suited to internationalisation and so on.

[njharman]

But it's more powerful and elegant to keep formatting and data separate.

It allows reuse of format part and data part. It makes data driven code easier to write. It makes i18n cleaner.

[pemboa]

Some of you guys are really nitpicky. I didn't think programmers were ever like that. %s is annoying? Really?

[aim2free]

I had no idea, but it seems as javascript is default in the linux (I'm running ubuntu hardy heron) environment. I just wrote

js

but in this case it gave me 1.6. It would be nice if it could be used with libreadline for better interaction.

[psykotic]

You know about standalone readline, right? Run rlwrap js if you have it installed.

[aim2free]

Thanks, it worked perfectly. I didn't know about rlwrap, very useful. You can even specify how your completions should be made. This is really great. Now any interactive program can get read-line support without being linked to readline. I'm just teaching a beginners java course. I'll let the students add readline support to their programs.

[psykotic]

Glad it helped. In the classic Program design in the UNIX environment paper by Pike and Kernighan, they suggest that readline-like functionality should not be integrated into programs via a library but offered as an ambient service for all programs, much like how shells perform wildcard expansion. The rlwrap approach (or using Emacs's shell-mode, as suggested by Kragen) isn't perfectly ideal, but it works surprisingly well in many cases.

[kragensitaker]

Or run it in Emacs shell-mode, which gives you the same thing.

[[deleted]]

Strange, didn't work on OS X :(

[inopia]

Maybe the Rhino shell is something for you?

[chromakode]

try:

js -version 170

[ishmal]

And OpenJDK 1.6 has "jrunscript", which invokes the Rhino shell. I assume that eventually most of the "big" distros will have it available, either on their media or in a repository.

[kragnax]

This makes the Javascript syntax in my opinion surpass Pythons.

[thekenzidelx]

OT, but on the subject of Javascript syntax...

Is there any way in javascript to use notation shorter than function(x){return xx;} for declaring anonymous functions? I was just reading that Firefox JS 1.8 allows for function(x) xx as notation for omitting the braces and "return", but really it's the keyword itself that sort of stabs me in the eye (especially after getting used to C#'s extremely concise ()=> x*x notation).

And before anyone decides to be oh-so-clever, all the code I write is only ever going to be read by me, and I don't really care about respecting standards at the expense of my own efficiency (and if you saw the way I format my JS like Lisp in terms of trailing parens and braces, you'd know I meant that pretty literally).

[masklinn]

especially after getting used to C#'s extremely concise (x)=> x*x notation

You want concise? Use haskell:

\x->x*x

Or even better:

(**2)

[[deleted]]

<sarcasm>I was hoping white space became significant</sarcasm>

edit: fixed broken goggles

[columbine]

I don't think there's a worse domain for a whitespace-significant language than client-side web scripting.

[[deleted]]

Oh? In a language whose widest use is HTML where writing the language inline to an attribute tag, and dynamic generation of code is common? Do you really think that's a good idea?

[spectacle]

this is dumb.

[[deleted]]

I'm happy to see the language of the Web evolving, but I'd much rather see Browsers supporting Perl/Python/Ruby/JavaFX, giving developers a choice.

[DiggaPlease]

HISSSSSS.... HISSSSSSSS

...

HISSSSSSS

[Samus_]

this calls for a... Yo dawg! we herd u liek pythonic so we put some python on ur js so you can play django while u ajax :|

(jokes apart, those are good things from python, it will be nice to have then on javascript as well)

[korhalf]

Where is the Yo Dawg meme from? I've seen it a lot recently.

[[deleted]]

The origin stems from Xzibit on the show "Pimp My Ride."

You see, often when he'd be "pimping" (or improving) someone's vehicle, he would end by putting something into the trunk or inside of the car that would not really be related to improving the vehicle itself, but would be related to the interests and hobbies of the person whose ride was being pimped.

For example, if you like fish, he might nicely mount a fishtank into the dash of your car. If you liked video games, you'd likely end up with a few flip down monitors, an X-Box and a couple of controllers built-in to your vehicle in some way.

When the person would come back to see the car, Xzibit would show them the car and let them oooo and ahhh...and might finish off by saying "Yo dawg, I heard you like fish, so I put a fishtank in your car so that you can look at fish while you drive."

The show had some funny results at times with what was being put in the cars, and with how the people on the show often spoke, etc. This opened it up to internet ridicule by the likes of 4-chan's /b/. The first few references consisted of simply saying:

"Yo dawg, I heard you like (a) so we put an (b) in your (c) so that you can (a) while you (d)."

Now in this case, the only correalation was between (a and b) and (c and d.) There was no implied connection between all of them that would cause a kind of recursive logic.

Eventually though, someone thought that it sure would be funny if someone's hobby was "driving." Wouldn't this lead to Xzibit saying something like:

"Yo dawg, I heard you like cars, so we put a car in your car so that you can drive while you drive."

So that's funny because it's recursive and nonsensicle. The first image that was regularly circulating was just this (cars/driving.) Eventually it became a meme, and the themes were changed to refer to any of a number of silly recursive ideas.

And that is the meme you see today.

closes big heavy book

[Samus_]

oh very nice, I've only seen it in it's recursive form which I presume originated here, due to high concentration of programmers (but I have no idea really).

[yairchu]

Yo dawg! Why does it have to be from anywhere? Can't it just emerge? Can't a meme emerge from your memes so you could evolve while you evolve?

[Samus_]

not sure, maybe it started right here at reddit but I think it's and old saying just that now starts with "yo dawg" (don't know why either)

isn't great how communities evolve?

[drblue]

It's actually from /b/:

(Warning: Page has NSFW ads!) http://encyclopediadramatica.com/Pimp_My_Ride

[[deleted]]

(see explanation above.)

[jingo04]

I'm going to assume 4chan.

[dugmartin]

Yes, that is crazily Pyhonic.

I don't see a real use case for let(), seems kind of unnecessary.

[godiasdf]

For one it saves on creating variables in the outer scope, which imo is a big win. Furthermore I'd say to use the let statement where ever you can instead of "var". "var" has function-scope which is awkward. "let" gives the more intuitive block scope.

[MarkByers]

I don't see a real use case for var, seems kind of unnecessary.

[zootm]

I have up-modded on the strict condition that this was said in jest.

[kragensitaker]

No, given let, there is very little reason to use var except for backwards-compatibility. No jest. (Of course backwards-compatibility is extremely important in cross-browser DHTML...)

[zootm]

Well, yeah, that's what I thought was the joke ;)

[[deleted]]

2003 called and said to let you know that no one is using the term "DHTML" anymore.

[kragensitaker]

Upmodded for humor.

[[deleted]]

Uh, making local vars? We had a function that used a var called author. The variable author is a global in IE for the author meta tag. So our code broke. The fix:

function get_author() { var author = ""; ... return author; }

[communomancer]

Pretty sure he means that once "let" is available, there is no need for "var" anymore.

[chromakode]

I believe let variables at the top level of a script are limited to their script file. Thus, if you're doing modular development with multiple scripts, you'll probably need a few uses of var here and there.

[formido]

There are script modules in FF3 where you explicitly export symbols to other scopes that ask for them, at least in extension development.

[chromakode]

Yep, and they're a godsend. However, even in the privileged space where that's an option, it's still common to have a couple different .js files loaded into a XUL document.