8 ms·

EcmaScript Sixth Edition

40 points by joeyespo 12y ago

VeejayRampay 12y ago
All those additions are welcome (and wayyyyyyyyy overdue to be honest) but something is striking me as quite old-fashioned : for (var [key, val] of items(x)) { alert(key + ',' + val); } That syntax isn't really natural, I would think something like: items(x).forEach(function(key, value) { alert(key + ',' + val); }); is more natural and readable. It also brings up the question of interpolation, why do we even have to use + in the first place? Also, can someone in the know care to tell me why that is that those additions for what is the end rather basic functionality is coming so late to the language?
- chuckup 12y ago
  >Also, can someone in the know care to tell me why that is that those additions for what is the end rather basic functionality is coming so late to the language? I would think Internet Explorer being the dominant browser had something to do with it.
- espadrine 12y ago
  Iterables can have many forms (Strings, Arrays, Maps…), so having a forEach method is tricky. On the other hand, most iterables have their own methods to loop around values. Arrays and Maps both have a .forEach() method.
- laughinghan 12y ago
  items(x).forEach(function(key, value) { alert(key + ',' + val); }); You can already just do that, without ES6. > It also brings up the question of interpolation, why do we even have to use + in the first place? Did you miss the last item, "quasis"? `You are ${age} years old.` > Also, can someone in the know care to tell me why that is that those additions for what is the end rather basic functionality is coming so late to the language? Because unlike most languages, there's no canonical implementation. Mozilla, who actually holds the trademark on the name "JavaScript", totally tried to evolve the language since the beginning and even shipped e.g. JavaScript 1.7 (which had generators, iterators, let, array comprehensions, and destructuring assignment [1]) with Firefox 2 in 2006, but Firefox just didn't have the market share for authors to start using the new features, and no other browser implemented any of them. That deadlock was only broken by Brendan Eich using corporate politics rather than hacker-style "putting it out there": rounding up all the big browser makers (of course, it helped that Apple and Google had just broken into the scene), and convincing them to commit to implementing new features decided on by the committee they formed, TC39 (and to update their browsers at all, ahem IE ahem). [1]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/New_in_JavaScript/1.7 https://developer.mozilla.org/en-US/docs/Web/JavaScript/New_...
  - VeejayRampay 12y ago
    Unless I'm missing something, you cannot use forEach on a Javascript object as of now (or map, reduce, every, some and other methods that are available on Array.prototype). The only way is to use: for(var key in obj) {...} As for interpolation, I indeed missed the bit about quasis. Though I really wonder why they would still use concatenation if they can interpolate... Maybe to only show one feature at a time, which I guess makes sense.
    - arcosdev 12y ago
      You are correct, there is no forEach, a lot of libraries implement their own, but no native version.
      - SimeVidas 12y ago
        Object.keys(obj).forEach(function (key) { var val = obj[key]; // use key and val here });
    - omaranto 12y ago
      I think you did miss something: the comment you replied to didn't say x.forEach(f); but rather items(x).forEach(x); which is definitely possible, you just need to implement items().
  - carussell 12y ago
    Sun/Oracle has always held the trademark on JavaScript, not Mozilla. And TC39 predates the "JavaScript Renaissance" that you're talking about.
    - laughinghan 12y ago
      "JavaScript is a trademark or registered trademark of Sun Microsystems, Inc. [...] used under license." https://www.mozilla.org/en-US/foundation/trademarks/list/ https://www.mozilla.org/en-US/foundation/trademarks/list/ TIL! And you're right about TC39, I probably should have said "joined", not "formed", if I could edit my comment I would. I don't think my comment was a gross misrepresentation of the historical context, though.
- gsnedders 12y ago
  > Also, can someone in the know care to tell me why that is that those additions for what is the end rather basic functionality is coming so late to the language? Back when IE was stagnating, when nobody was working on anything more than maintaining IE6, TC-39 (the technical committee that works on ECMAScript) was working towards a 4th revision of the standard (i.e., ES4), incorporating a lot of quite reasonable things (like the above) but also quite a lot of things based on very recent research. There was pushback against quite so aggressively moving forward in a single revision, especially incorporating so much from academia not already proven elsewhere (the browser space is very conservative about breaking existing content, so if something that turned out to be a bad idea shipped, it'd be very very hard to get rid of). In the end, there was relatively significant pushback once MS reappeared from themselves, Yahoo, and a number of other contributors. Moving forward, the plan was essentially to tidy up the ES3 spec with minor additions, which was originally referred to as ES3.1 but eventually standardised as ES5. ES6 is the next revision of this branch of the standard. ActionScript 3, as Flash uses, is based on one of the drafts of ES4, and prior to the abandonment of Flash development, the intention was to continue to evolve the language separately to ECMAScript.
yoanizer 12y ago
Ok but when can we expect to start using that and have our web apps work in the real world? in 10 years? 20 years?
- CmonDev 12y ago
  ~10 years.
- VeejayRampay 12y ago
  Much faster if you are willing to punish your users for using subpar browsers that don't keep up with current technologies and standards. A bullet I retrospectively think we should have bit a long time ago. It would have sent a strong message that you either make sure that your browser is top notch or it will be left behind to bite the dust of the power horses. Now that Microsoft is feeling the heat under its ass (from FF, Chrome and Safari), they're making sure IE is not ridiculously worse than the competition, that it auto-updates, they're engaging the community, creating libraries, etc.
  - yoanizer 12y ago
    I can't even think about blaming my Clients for not using the latest IE because I want to use some syntax sugar for things that I can already do with ECMA 5.
    - VeejayRampay 12y ago
      That's not what I'm saying. I'm talking about 5 years ago when IE7/IE8 were lagging behind by a HUGE margin and it was another world trying to make things compatible. It was not a matter of using the last version, it was a matter of Microsoft not paying attention or not wanting to make its flagship browser better. Not just some developer throwing a fit because he needed "sugar". Also, and that's only personal opinion, but there's a limit to the customer is always right. What if we create a new super highway one day with flying cars, are we going to punt on moving on because some people like their combustion engine pieces of junk? It's also our jobs to make people understand that jumping on the latest technology is in their best interest. Leveling the field to the lowest common denominator brings everyone down in the end and really hampers creation and innovation. And that is the reason why Javascript is so far behind modern languages in so many areas.
szatkus 12y ago
Awesome! Most of these things works under Firefox if you want to play.
lukasm 12y ago
Great summary. Any breaking changes?
- TazeTSchnitzel 12y ago
  No.
- jarek-foksa 12y ago
  In ES6 "typeof null" will give you "null" rather than "object". There were also some talks on making "__proto__" non-mutable, but I'm not sure whether this breaking change made it into the spec.
TazeTSchnitzel 12y ago
> fat arrow: (a) => a * a is the same as function(a) { return a * a; } No, it's equivalent to the following: (function (a) { return a * a; }).bind(this); The fat arrow has lexically scoped this. On an entirely different note, I never liked how generators are marked with an asterisk. A generator isn't special, it is just a function returning an iterator. A generator should be able to return normally as well as yield.
- espadrine 12y ago
  You're absolutely right! Fixed, thanks! (PS, repository is here: https://github.com/espadrine/New-In-A-Spec https://github.com/espadrine/New-In-A-Spec)
- pimterry 12y ago
  Generators have to be marked as an asterisk as otherwise there's ambiguity; until recently 'yield' wasn't a reserved word, so it might be a variable name or anything. Without disambiguating (via the *) old JavaScript can potentially break.
  - untothebreach 12y ago
    'yield' was a reserved word in the ES4 spec, and a 'FutureReservedWord' in ES5 so if there is code that uses it as an identifier, it has been technically broken since 2008...
    - gsnedders 12y ago
      What ES4 says is irrelevant. yield is only a FutureReservedWord in ES5 when within strict mode code; in non-strict code it is not a keyword, and plenty of code uses it and works in ES5 implementations.
- ptx 12y ago
  > A generator isn't special, it is just a function returning an iterator. A generator should be able to return normally as well as yield. But in a generator function the iterator is returned immediately, before any of the code in the function runs, so how would it return anything else? For example: function* f() { console.log("function commencing!"); for (x of [1, 2, 3]) { console.log("yielding " + x); yield x; } } var it = f(); console.log("iterator returned from function:", it); console.log(it.next().value); would print: "iterator returned from function:" Generator { } Scratchpad/1:19 "function commencing!" Scratchpad/1:11 "yielding 1" Scratchpad/1:13 1 So even if the very first thing the function does is if (isTuesday()) return something; else yield somethingElse; ...by that point it would have already returned an iterator, so it would be too late to decide otherwise, wouldn't it?
deleted 12y ago
[deleted]
snorkel 12y ago
Please stop evolving Ecmascript. If this continues then soon JavaScript will have gone from a nice simple, elegant language into C++ 11, incomprehensible to both humans and machines, and then the replacement languages will start to proliferate, fragmentation, ugh ... Let's just agree that JavaScript only needs minor enhancements, not mind bending magical operators and keywords. Please don't do to JavaScript what perl6 did to perl. If you want a mind numbing language then please use Haskell or erlang, and let JavaScript remain simple.
- igl 12y ago
  I completely agree. It's like they did not learn from javascripts mistakes and just continue doing them. Global Scope: not fixed. No integer: not fixed. Syntax to resemble JAVA more closely in a class-less language that already as 9999999999999 class libraries: FIXED
  - gsnedders 12y ago
    How can you fix the global scope without breaking almost all existing JS code? Browsers will never ship anything that breaks large numbers of existing websites (users don't use browsers that don't work with the web!). Adding an integer type is far easier said than done. It was decided to leave that hard problem to ES7; integer type (or types!) are certainly coming.
    - BugBrother 12y ago
      >> How can you fix [X] without breaking almost all existing [Y] code? For most cases of X, some form of declaration that is scope bound. Look at e.g. Perl, it changes quickly in this way, with very good backwards compatibility. [Also see strict mode, of course.] Edit: That said, new keywords like those let/const/module/extends etc should work fine. Please give me them today. Edit 2: I have been cursing the lack of multiple returns this week. It is a pain returning a hash/object or an array. That really isn't supported, from browsing the standard? :-(
      - 12y ago
adrusi 12y ago
> array and generator comprehension: [a+b for (a in A) for (b in B)] (array comprehension), (x for (x of generateValues()) if (x.color === 'blue')) (generator expression). Bit of an error here. The array comprehension uses "in" which will iterate over the indexes of A and B. While this is technically valid, no one would look at that and expect it to return the string concatenation of all the indexes of A and B :)
- espadrine 12y ago
  You're right; I didn't update the example while the syntax was in flux. Fixed! ☺ (There's no certainty that the syntax will be kept, though, see this[1] about deferring it to ES7 to generalize the syntax for parallelism, and this[2] to make async promises and generators work together.) [1]: https://speakerdeck.com/dherman/a-better-future-for-comprehensions https://speakerdeck.com/dherman/a-better-future-for-comprehe... [2]: https://docs.google.com/file/d/0B4PVbLpUIdzoMDR5dWstRllXblU/edit https://docs.google.com/file/d/0B4PVbLpUIdzoMDR5dWstRllXblU/...

40 points by joeyespo 12y ago

All those additions are welcome (and wayyyyyyyyy overdue to be honest) but something is striking me as quite old-fashioned : for (var [key, val] of items(x)) { alert(key + ',' + val); } That syntax isn't really natural, I would think something like: items(x).forEach(function(key, value) { alert(key + ',' + val); }); is more natural and readable. It also brings up the question of interpolation, why do we even have to use + in the first place? Also, can someone in the know care to tell me why that is that those additions for what is the end rather basic functionality is coming so late to the language?

chuckup 12y ago
>Also, can someone in the know care to tell me why that is that those additions for what is the end rather basic functionality is coming so late to the language? I would think Internet Explorer being the dominant browser had something to do with it.
espadrine 12y ago
Iterables can have many forms (Strings, Arrays, Maps…), so having a forEach method is tricky. On the other hand, most iterables have their own methods to loop around values. Arrays and Maps both have a .forEach() method.
laughinghan 12y ago
items(x).forEach(function(key, value) { alert(key + ',' + val); }); You can already just do that, without ES6. > It also brings up the question of interpolation, why do we even have to use + in the first place? Did you miss the last item, "quasis"? `You are ${age} years old.` > Also, can someone in the know care to tell me why that is that those additions for what is the end rather basic functionality is coming so late to the language? Because unlike most languages, there's no canonical implementation. Mozilla, who actually holds the trademark on the name "JavaScript", totally tried to evolve the language since the beginning and even shipped e.g. JavaScript 1.7 (which had generators, iterators, let, array comprehensions, and destructuring assignment [1]) with Firefox 2 in 2006, but Firefox just didn't have the market share for authors to start using the new features, and no other browser implemented any of them. That deadlock was only broken by Brendan Eich using corporate politics rather than hacker-style "putting it out there": rounding up all the big browser makers (of course, it helped that Apple and Google had just broken into the scene), and convincing them to commit to implementing new features decided on by the committee they formed, TC39 (and to update their browsers at all, ahem IE ahem). [1]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/New_in_JavaScript/1.7 https://developer.mozilla.org/en-US/docs/Web/JavaScript/New_...
- VeejayRampay 12y ago
  Unless I'm missing something, you cannot use forEach on a Javascript object as of now (or map, reduce, every, some and other methods that are available on Array.prototype). The only way is to use: for(var key in obj) {...} As for interpolation, I indeed missed the bit about quasis. Though I really wonder why they would still use concatenation if they can interpolate... Maybe to only show one feature at a time, which I guess makes sense.
  - arcosdev 12y ago
    You are correct, there is no forEach, a lot of libraries implement their own, but no native version.
    - SimeVidas 12y ago
      Object.keys(obj).forEach(function (key) { var val = obj[key]; // use key and val here });
  - omaranto 12y ago
    I think you did miss something: the comment you replied to didn't say x.forEach(f); but rather items(x).forEach(x); which is definitely possible, you just need to implement items().
- carussell 12y ago
  Sun/Oracle has always held the trademark on JavaScript, not Mozilla. And TC39 predates the "JavaScript Renaissance" that you're talking about.
  - laughinghan 12y ago
    "JavaScript is a trademark or registered trademark of Sun Microsystems, Inc. [...] used under license." https://www.mozilla.org/en-US/foundation/trademarks/list/ https://www.mozilla.org/en-US/foundation/trademarks/list/ TIL! And you're right about TC39, I probably should have said "joined", not "formed", if I could edit my comment I would. I don't think my comment was a gross misrepresentation of the historical context, though.
gsnedders 12y ago
> Also, can someone in the know care to tell me why that is that those additions for what is the end rather basic functionality is coming so late to the language? Back when IE was stagnating, when nobody was working on anything more than maintaining IE6, TC-39 (the technical committee that works on ECMAScript) was working towards a 4th revision of the standard (i.e., ES4), incorporating a lot of quite reasonable things (like the above) but also quite a lot of things based on very recent research. There was pushback against quite so aggressively moving forward in a single revision, especially incorporating so much from academia not already proven elsewhere (the browser space is very conservative about breaking existing content, so if something that turned out to be a bad idea shipped, it'd be very very hard to get rid of). In the end, there was relatively significant pushback once MS reappeared from themselves, Yahoo, and a number of other contributors. Moving forward, the plan was essentially to tidy up the ES3 spec with minor additions, which was originally referred to as ES3.1 but eventually standardised as ES5. ES6 is the next revision of this branch of the standard. ActionScript 3, as Flash uses, is based on one of the drafts of ES4, and prior to the abandonment of Flash development, the intention was to continue to evolve the language separately to ECMAScript.

yoanizer 12y ago

Ok but when can we expect to start using that and have our web apps work in the real world? in 10 years? 20 years?

CmonDev 12y ago
~10 years.
VeejayRampay 12y ago
Much faster if you are willing to punish your users for using subpar browsers that don't keep up with current technologies and standards. A bullet I retrospectively think we should have bit a long time ago. It would have sent a strong message that you either make sure that your browser is top notch or it will be left behind to bite the dust of the power horses. Now that Microsoft is feeling the heat under its ass (from FF, Chrome and Safari), they're making sure IE is not ridiculously worse than the competition, that it auto-updates, they're engaging the community, creating libraries, etc.
- yoanizer 12y ago
  I can't even think about blaming my Clients for not using the latest IE because I want to use some syntax sugar for things that I can already do with ECMA 5.
  - VeejayRampay 12y ago
    That's not what I'm saying. I'm talking about 5 years ago when IE7/IE8 were lagging behind by a HUGE margin and it was another world trying to make things compatible. It was not a matter of using the last version, it was a matter of Microsoft not paying attention or not wanting to make its flagship browser better. Not just some developer throwing a fit because he needed "sugar". Also, and that's only personal opinion, but there's a limit to the customer is always right. What if we create a new super highway one day with flying cars, are we going to punt on moving on because some people like their combustion engine pieces of junk? It's also our jobs to make people understand that jumping on the latest technology is in their best interest. Leveling the field to the lowest common denominator brings everyone down in the end and really hampers creation and innovation. And that is the reason why Javascript is so far behind modern languages in so many areas.

szatkus 12y ago

Awesome! Most of these things works under Firefox if you want to play.

lukasm 12y ago

Great summary. Any breaking changes?

TazeTSchnitzel 12y ago
No.
jarek-foksa 12y ago
In ES6 "typeof null" will give you "null" rather than "object". There were also some talks on making "__proto__" non-mutable, but I'm not sure whether this breaking change made it into the spec.

TazeTSchnitzel 12y ago

> fat arrow: (a) => a * a is the same as function(a) { return a * a; } No, it's equivalent to the following: (function (a) { return a * a; }).bind(this); The fat arrow has lexically scoped this. On an entirely different note, I never liked how generators are marked with an asterisk. A generator isn't special, it is just a function returning an iterator. A generator should be able to return normally as well as yield.

espadrine 12y ago
You're absolutely right! Fixed, thanks! (PS, repository is here: https://github.com/espadrine/New-In-A-Spec https://github.com/espadrine/New-In-A-Spec)
pimterry 12y ago
Generators have to be marked as an asterisk as otherwise there's ambiguity; until recently 'yield' wasn't a reserved word, so it might be a variable name or anything. Without disambiguating (via the *) old JavaScript can potentially break.
- untothebreach 12y ago
  'yield' was a reserved word in the ES4 spec, and a 'FutureReservedWord' in ES5 so if there is code that uses it as an identifier, it has been technically broken since 2008...
  - gsnedders 12y ago
    What ES4 says is irrelevant. yield is only a FutureReservedWord in ES5 when within strict mode code; in non-strict code it is not a keyword, and plenty of code uses it and works in ES5 implementations.
ptx 12y ago
> A generator isn't special, it is just a function returning an iterator. A generator should be able to return normally as well as yield. But in a generator function the iterator is returned immediately, before any of the code in the function runs, so how would it return anything else? For example: function* f() { console.log("function commencing!"); for (x of [1, 2, 3]) { console.log("yielding " + x); yield x; } } var it = f(); console.log("iterator returned from function:", it); console.log(it.next().value); would print: "iterator returned from function:" Generator { } Scratchpad/1:19 "function commencing!" Scratchpad/1:11 "yielding 1" Scratchpad/1:13 1 So even if the very first thing the function does is if (isTuesday()) return something; else yield somethingElse; ...by that point it would have already returned an iterator, so it would be too late to decide otherwise, wouldn't it?

deleted 12y ago

[deleted]

snorkel 12y ago

Please stop evolving Ecmascript. If this continues then soon JavaScript will have gone from a nice simple, elegant language into C++ 11, incomprehensible to both humans and machines, and then the replacement languages will start to proliferate, fragmentation, ugh ... Let's just agree that JavaScript only needs minor enhancements, not mind bending magical operators and keywords. Please don't do to JavaScript what perl6 did to perl. If you want a mind numbing language then please use Haskell or erlang, and let JavaScript remain simple.

igl 12y ago
I completely agree. It's like they did not learn from javascripts mistakes and just continue doing them. Global Scope: not fixed. No integer: not fixed. Syntax to resemble JAVA more closely in a class-less language that already as 9999999999999 class libraries: FIXED
- gsnedders 12y ago
  How can you fix the global scope without breaking almost all existing JS code? Browsers will never ship anything that breaks large numbers of existing websites (users don't use browsers that don't work with the web!). Adding an integer type is far easier said than done. It was decided to leave that hard problem to ES7; integer type (or types!) are certainly coming.
  - BugBrother 12y ago
    >> How can you fix [X] without breaking almost all existing [Y] code? For most cases of X, some form of declaration that is scope bound. Look at e.g. Perl, it changes quickly in this way, with very good backwards compatibility. [Also see strict mode, of course.] Edit: That said, new keywords like those let/const/module/extends etc should work fine. Please give me them today. Edit 2: I have been cursing the lack of multiple returns this week. It is a pain returning a hash/object or an array. That really isn't supported, from browsing the standard? :-(
    - 12y ago

adrusi 12y ago

> array and generator comprehension: [a+b for (a in A) for (b in B)] (array comprehension), (x for (x of generateValues()) if (x.color === 'blue')) (generator expression). Bit of an error here. The array comprehension uses "in" which will iterate over the indexes of A and B. While this is technically valid, no one would look at that and expect it to return the string concatenation of all the indexes of A and B :)

espadrine 12y ago
You're right; I didn't update the example while the syntax was in flux. Fixed! ☺ (There's no certainty that the syntax will be kept, though, see this[1] about deferring it to ES7 to generalize the syntax for parallelism, and this[2] to make async promises and generators work together.) [1]: https://speakerdeck.com/dherman/a-better-future-for-comprehensions https://speakerdeck.com/dherman/a-better-future-for-comprehe... [2]: https://docs.google.com/file/d/0B4PVbLpUIdzoMDR5dWstRllXblU/edit https://docs.google.com/file/d/0B4PVbLpUIdzoMDR5dWstRllXblU/...