9 ms·

New ES2019 JavaScript features

92 points by ducaale 7y ago

dlojudice 7y ago
JS is going to be so different in 2019 that I'm expecting a revised version of "The Good Parts"[1] [1] https://www.amazon.com/JavaScript-Good-Parts-Douglas-Crockford/dp/0596517742 https://www.amazon.com/JavaScript-Good-Parts-Douglas-Crockfo...
- eropple 7y ago
  That book is of an era and hasn't been particularly relevant in quite awhile. The rise of classes as prototype sugar made a lot of the navel-gazing of object creation mostly moot. The rise of rigorous linting took care of the rest. TypeScript helped a lot, too.
  - Roboprog 7y ago
    Some of us consider “class” a bad thing. I would rather work in a language/style that draws its inspiration from Scheme than Simula 67. Too bad more places are picking up TypeScript rather than ClosureScript.
    - orangecat 7y ago
      I would rather work in a language/style that draws its inspiration from Scheme than Simula 67. Then you should push for WebAssembly improvements so you can use whatever language you want. As long as JavaScript is a de facto requirement for web development it needs to be as approachable as possible to a wide developer audience, and that means looking more like Java than Lisp.
      - BigJono 7y ago
        Or we could've considered it an opportunity to move people away from classical inheritance and towards something that's conceptually much simpler? (which both prototypal inheritance and functional programming are)
        pjmlp 7y ago
        Yet all successful functional programming languages do support doing OOP as well.
        boomlinde 7y ago
        JS is and always was prototype based. The class keyword is as far as I know just syntax sugar that creates a prototype chain and a new-able function that assigns the prototype to self.
        jwalton 7y ago
        The '#privateVar' syntax means that classes are no longer simply syntax sugar, unfortunately.
        eropple 7y ago
        Private variables could always be simulated with IIFEs. I'm pretty sure that's actually how TypeScript does it if you compile down low enough.
      - jcadam 7y ago
        > and that means looking more like Java than Lisp. No. (No (No (No (No (No)))))
    - nine_k 7y ago
      Classes are fine! Inheritance isn't. You can mostly avoid using it, though. JS lacks homoiconicity and thus can't have a lot of nice things a Lisp dialect would, notably macros. With what we've got, I have more hope on JS eventually migrating towards a (more) statically typed language with ML influence; typescript sort of leans towards it, slowly.
      - sli 7y ago
        You're right about Lisp features, but CLJS macros are kind of bad at the moment. I have a fairly simple macro that works just fine in Clojure but does not compile in ClojureScript and I can't figure out why. It's probably a side-effect of how macros are handled in CLJS (they're part of a different compilation stage and must be written in CLJ or CLJC, hence :require-macros instead of just :require). If you're looking for an ML, check out ReasonML. It's really quite good, its output is quite good (and hotfix friendly), and its type system is far better than TypeScript's will ever be. Mostly because TS wants to stay close to JS. Too close, in my opinion.
    - eropple 7y ago
      You can consider it a bad thing, but 1) it's a really thin layer on top of prototypical inheritance, 2) it makes JavaScript more accessible to people who are used to conventional styles of language, and 3) it won, indisputably. ClojureScript didn't win, and never had a chance to win, because it's written for the small minority of Clojure people. It wasn't written for the overwhelming majority of developers. TypeScript was. So sorry that the existence of those day-to-day programmers puts a crimp in your utopia, but, enh. Personally, I'm glad we have tools to make it easier to write libraries to help that majority be more productive and to make their code safer and more correct!
    - sli 7y ago
      It really is a shame because ClojureScript is an absolute joy to work with. TypeScript and Javascript feel so incredibly tedious to write after using CLJS for a few months. I would really love to move into PureScript as well, but I haven't quite wrapped my arms around Haskell as a whole, yet. So maybe I should tip my toes back into Elm for a bit.
  - jcadam 7y ago
    I do not use the 'class' keyword in Javascript and I never will. I mean, I don't like using it in Java either, but it isn't really optional there...
    - stevula 7y ago
      Not optional for React devs. Well... maybe now with hooks.
baron816 7y ago
Why is the pipeline operator mentioned here? That’s definitely not ES2019.
- SSchick 7y ago
  Yea, I was thinking the same, it's not even on https://github.com/tc39/proposals https://github.com/tc39/proposals
  - lhorie 7y ago
    Stage 1 proposals were moved to a separate page, presumably to reduce clutter https://github.com/tc39/proposals/blob/master/stage-1-proposals.md https://github.com/tc39/proposals/blob/master/stage-1-propos...
randallsquared 7y ago
This seems like a better guide to actual ES2019: https://medium.com/@selvaganesh93/javascript-whats-new-in-ecmascript-2019-es2019-es10-35210c6e7f4b https://medium.com/@selvaganesh93/javascript-whats-new-in-ec...
lhorie 7y ago
FYI, the ES2019 spec has been published[1] already and optional chaining and pipeline operator are not in it. If you want to know what's new in ES2019, look no further than the [Introduction](https://www.ecma-international.org/ecma-262/10.0/index.html#sec-intro https://www.ecma-international.org/ecma-262/10.0/index.html#...) section in the spec. > This specification, the 10th edition, introduces a few new built-in functions: flat and flatMap on Array.prototype for flattening arrays, Object.fromEntries for directly turning the return value of Object.entries into a new Object, and trimStart and trimEnd on String.prototype as better-named alternatives to the widely implemented but non-standard String.prototype.trimLeft and trimRight built-ins. In addition, this specification includes a few minor updates to syntax and semantics. Updated syntax includes optional catch binding parameters and allowing U+2028 (LINE SEPARATOR) and U+2029 (PARAGRAPH SEPARATOR) in string literals to align with JSON. Other updates include requiring that Array.prototype.sort be a stable sort, requiring that JSON.stringify return well-formed UTF-8 regardless of input, and clarifying Function.prototype.toString by requiring that it either return the corresponding original source text or a standard placeholder. [1] https://www.ecma-international.org/ecma-262/10.0/index.html https://www.ecma-international.org/ecma-262/10.0/index.html
- robotstate 7y ago
  Of course the two features I was most excited about aren't in the actual spec...
STRiDEX 7y ago
I always use http://node.green http://node.green because it also tells me if I can use it yet/soon.
- zaro 7y ago
  Thanks. I've wondered recently how to check what is supported in node.
Roboprog 7y ago
Thanks for links to accurate information, those who posted TL;DR - most of what is added in 2019 I can already do with Ramda.js, and it works in IE11, as well. Pity about the Ruby / Groovy style dot-condition-chaining NOT being in the 2019 features, though.
atonse 7y ago
As a former C# dev, I’m excited about the optionals. As a current elixir dev, VERY excited about the pipe operator.
- nojvek 7y ago
  Chaining operator is likely to land. V8 has optional support for it and Babel has some plugins. Pipeline operator has lots of quirks and syntax bikeshedding. I don’t think it may land. Especially when you can make your own pipe(x,y,z) function quite easily. Just a guess though.
crooked-v 7y ago
The pipe operator is the key thing I'm really looking forward to as a general quality of life improvement.
Bjartr 7y ago
Wait, trimLeft/trimRight has different semantics from trimStart/trimEnd in RTL languages. So it has to be more than a simple alias, right?
- lioeters 7y ago
  I checked on MDN: "The trimStart() method removes whitespace from the beginning of a string. trimLeft() is an alias of this method." https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/trimStart https://developer.mozilla.org/en-US/docs/Web/JavaScript/Refe... I suspect that trimLeft was misnamed, since its "left" didn't take into account RTL - it just meant start of string.
a13n 7y ago
Super duper excited about optional chaining! One thing I miss from Objective-C that I wish JS would add is the `?:` operator – basically a shortened version of the ternary operator.
- saagarjha 7y ago
  I think that's a GCC C extension, not an Objective-C feature.
  - a13n 7y ago
    Sure, I still miss it from Objective-C :P
- strbean 7y ago
  How would this differ from the idiomatic "x || y"? Just s/non-zero/truthy
  - deleted 7y ago
    [deleted]
  - nojvek 7y ago
    || short circuits on falsey. 0, “”, false, null, undefined ?? Short circuits on nullish. Only null and undefined.
- rmrfrmrf 7y ago
  Optional chaining is moving through committee along with the "nullish coalescing operator" represented as `??`, which works like `||` except only falls through with `null` and `undefined`.
- kamyarg 7y ago
  Do you mean true ? console.log("foo") : console.log("bar") ? This is already there: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Conditional_Operator https://developer.mozilla.org/en-US/docs/Web/JavaScript/Refe...
hpen 7y ago
woooh optional chaining!
rkwz 7y ago
I wish there was more focus on increasing the surface area of the standard library instead of more language features like Golang
RobertKerans 7y ago
This is a very minor frustration, and I'm screaming into the abyss, but when searching for JavaScript topics, blogposts from LogRocket pretty often come up top of the search rankings, above more authoritative sources. Often under slightly misleading titles (such as this one) that seem chosen to capitalise on common search terms, or else the articles are packed with keywords. Sometimes mildly useful but mostly they're shallow and not particularly contentful, and LogRocket seem to absolutely churn them out. Seems to have gone down slightly since moving from Medium to Hosted WP, but not much. Nothing doing, it's just SEO and getting the name "LogRocket" in front of more eyeballs, but just...urrgh
11235813213455 7y ago
> pipeline operator no thanks, I don't think it's an interesting feature, there are alternatives (chaining, promises, ..) to avoid the cost of this new syntax Other proposals I'm more excited about: - https://github.com/tc39/proposal-iterator-helpers https://github.com/tc39/proposal-iterator-helpers - https://github.com/tc39/proposal-slice-notation/ https://github.com/tc39/proposal-slice-notation/ (and https://github.com/tc39/proposal-slice-notation/pull/32 https://github.com/tc39/proposal-slice-notation/pull/32)

92 points by ducaale 7y ago

JS is going to be so different in 2019 that I'm expecting a revised version of "The Good Parts"[1] [1] https://www.amazon.com/JavaScript-Good-Parts-Douglas-Crockford/dp/0596517742 https://www.amazon.com/JavaScript-Good-Parts-Douglas-Crockfo...

eropple 7y ago
That book is of an era and hasn't been particularly relevant in quite awhile. The rise of classes as prototype sugar made a lot of the navel-gazing of object creation mostly moot. The rise of rigorous linting took care of the rest. TypeScript helped a lot, too.
- Roboprog 7y ago
  Some of us consider “class” a bad thing. I would rather work in a language/style that draws its inspiration from Scheme than Simula 67. Too bad more places are picking up TypeScript rather than ClosureScript.
  - orangecat 7y ago
    I would rather work in a language/style that draws its inspiration from Scheme than Simula 67. Then you should push for WebAssembly improvements so you can use whatever language you want. As long as JavaScript is a de facto requirement for web development it needs to be as approachable as possible to a wide developer audience, and that means looking more like Java than Lisp.
    - BigJono 7y ago
      Or we could've considered it an opportunity to move people away from classical inheritance and towards something that's conceptually much simpler? (which both prototypal inheritance and functional programming are)
      - pjmlp 7y ago
        Yet all successful functional programming languages do support doing OOP as well.
      - boomlinde 7y ago
        JS is and always was prototype based. The class keyword is as far as I know just syntax sugar that creates a prototype chain and a new-able function that assigns the prototype to self.
        jwalton 7y ago
        The '#privateVar' syntax means that classes are no longer simply syntax sugar, unfortunately.
        eropple 7y ago
        Private variables could always be simulated with IIFEs. I'm pretty sure that's actually how TypeScript does it if you compile down low enough.
    - jcadam 7y ago
      > and that means looking more like Java than Lisp. No. (No (No (No (No (No)))))
  - nine_k 7y ago
    Classes are fine! Inheritance isn't. You can mostly avoid using it, though. JS lacks homoiconicity and thus can't have a lot of nice things a Lisp dialect would, notably macros. With what we've got, I have more hope on JS eventually migrating towards a (more) statically typed language with ML influence; typescript sort of leans towards it, slowly.
    - sli 7y ago
      You're right about Lisp features, but CLJS macros are kind of bad at the moment. I have a fairly simple macro that works just fine in Clojure but does not compile in ClojureScript and I can't figure out why. It's probably a side-effect of how macros are handled in CLJS (they're part of a different compilation stage and must be written in CLJ or CLJC, hence :require-macros instead of just :require). If you're looking for an ML, check out ReasonML. It's really quite good, its output is quite good (and hotfix friendly), and its type system is far better than TypeScript's will ever be. Mostly because TS wants to stay close to JS. Too close, in my opinion.
  - eropple 7y ago
    You can consider it a bad thing, but 1) it's a really thin layer on top of prototypical inheritance, 2) it makes JavaScript more accessible to people who are used to conventional styles of language, and 3) it won, indisputably. ClojureScript didn't win, and never had a chance to win, because it's written for the small minority of Clojure people. It wasn't written for the overwhelming majority of developers. TypeScript was. So sorry that the existence of those day-to-day programmers puts a crimp in your utopia, but, enh. Personally, I'm glad we have tools to make it easier to write libraries to help that majority be more productive and to make their code safer and more correct!
  - sli 7y ago
    It really is a shame because ClojureScript is an absolute joy to work with. TypeScript and Javascript feel so incredibly tedious to write after using CLJS for a few months. I would really love to move into PureScript as well, but I haven't quite wrapped my arms around Haskell as a whole, yet. So maybe I should tip my toes back into Elm for a bit.
- jcadam 7y ago
  I do not use the 'class' keyword in Javascript and I never will. I mean, I don't like using it in Java either, but it isn't really optional there...
  - stevula 7y ago
    Not optional for React devs. Well... maybe now with hooks.

baron816 7y ago

Why is the pipeline operator mentioned here? That’s definitely not ES2019.

SSchick 7y ago
Yea, I was thinking the same, it's not even on https://github.com/tc39/proposals https://github.com/tc39/proposals
- lhorie 7y ago
  Stage 1 proposals were moved to a separate page, presumably to reduce clutter https://github.com/tc39/proposals/blob/master/stage-1-proposals.md https://github.com/tc39/proposals/blob/master/stage-1-propos...

randallsquared 7y ago

This seems like a better guide to actual ES2019: https://medium.com/@selvaganesh93/javascript-whats-new-in-ecmascript-2019-es2019-es10-35210c6e7f4b https://medium.com/@selvaganesh93/javascript-whats-new-in-ec...

lhorie 7y ago

FYI, the ES2019 spec has been published[1] already and optional chaining and pipeline operator are not in it. If you want to know what's new in ES2019, look no further than the [Introduction](https://www.ecma-international.org/ecma-262/10.0/index.html#sec-intro https://www.ecma-international.org/ecma-262/10.0/index.html#...) section in the spec. > This specification, the 10th edition, introduces a few new built-in functions: flat and flatMap on Array.prototype for flattening arrays, Object.fromEntries for directly turning the return value of Object.entries into a new Object, and trimStart and trimEnd on String.prototype as better-named alternatives to the widely implemented but non-standard String.prototype.trimLeft and trimRight built-ins. In addition, this specification includes a few minor updates to syntax and semantics. Updated syntax includes optional catch binding parameters and allowing U+2028 (LINE SEPARATOR) and U+2029 (PARAGRAPH SEPARATOR) in string literals to align with JSON. Other updates include requiring that Array.prototype.sort be a stable sort, requiring that JSON.stringify return well-formed UTF-8 regardless of input, and clarifying Function.prototype.toString by requiring that it either return the corresponding original source text or a standard placeholder. [1] https://www.ecma-international.org/ecma-262/10.0/index.html https://www.ecma-international.org/ecma-262/10.0/index.html

robotstate 7y ago
Of course the two features I was most excited about aren't in the actual spec...

STRiDEX 7y ago

I always use http://node.green http://node.green because it also tells me if I can use it yet/soon.

zaro 7y ago
Thanks. I've wondered recently how to check what is supported in node.

Roboprog 7y ago

Thanks for links to accurate information, those who posted TL;DR - most of what is added in 2019 I can already do with Ramda.js, and it works in IE11, as well. Pity about the Ruby / Groovy style dot-condition-chaining NOT being in the 2019 features, though.

atonse 7y ago

As a former C# dev, I’m excited about the optionals. As a current elixir dev, VERY excited about the pipe operator.

nojvek 7y ago
Chaining operator is likely to land. V8 has optional support for it and Babel has some plugins. Pipeline operator has lots of quirks and syntax bikeshedding. I don’t think it may land. Especially when you can make your own pipe(x,y,z) function quite easily. Just a guess though.

crooked-v 7y ago

The pipe operator is the key thing I'm really looking forward to as a general quality of life improvement.

Bjartr 7y ago

Wait, trimLeft/trimRight has different semantics from trimStart/trimEnd in RTL languages. So it has to be more than a simple alias, right?

lioeters 7y ago
I checked on MDN: "The trimStart() method removes whitespace from the beginning of a string. trimLeft() is an alias of this method." https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/trimStart https://developer.mozilla.org/en-US/docs/Web/JavaScript/Refe... I suspect that trimLeft was misnamed, since its "left" didn't take into account RTL - it just meant start of string.

a13n 7y ago

Super duper excited about optional chaining! One thing I miss from Objective-C that I wish JS would add is the `?:` operator – basically a shortened version of the ternary operator.

saagarjha 7y ago
I think that's a GCC C extension, not an Objective-C feature.
- a13n 7y ago
  Sure, I still miss it from Objective-C :P
strbean 7y ago
How would this differ from the idiomatic "x || y"? Just s/non-zero/truthy
- deleted 7y ago
  [deleted]
- nojvek 7y ago
  || short circuits on falsey. 0, “”, false, null, undefined ?? Short circuits on nullish. Only null and undefined.
rmrfrmrf 7y ago
Optional chaining is moving through committee along with the "nullish coalescing operator" represented as `??`, which works like `||` except only falls through with `null` and `undefined`.
kamyarg 7y ago
Do you mean true ? console.log("foo") : console.log("bar") ? This is already there: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Conditional_Operator https://developer.mozilla.org/en-US/docs/Web/JavaScript/Refe...

hpen 7y ago

woooh optional chaining!

rkwz 7y ago

I wish there was more focus on increasing the surface area of the standard library instead of more language features like Golang

RobertKerans 7y ago

This is a very minor frustration, and I'm screaming into the abyss, but when searching for JavaScript topics, blogposts from LogRocket pretty often come up top of the search rankings, above more authoritative sources. Often under slightly misleading titles (such as this one) that seem chosen to capitalise on common search terms, or else the articles are packed with keywords. Sometimes mildly useful but mostly they're shallow and not particularly contentful, and LogRocket seem to absolutely churn them out. Seems to have gone down slightly since moving from Medium to Hosted WP, but not much. Nothing doing, it's just SEO and getting the name "LogRocket" in front of more eyeballs, but just...urrgh

11235813213455 7y ago

> pipeline operator no thanks, I don't think it's an interesting feature, there are alternatives (chaining, promises, ..) to avoid the cost of this new syntax Other proposals I'm more excited about: - https://github.com/tc39/proposal-iterator-helpers https://github.com/tc39/proposal-iterator-helpers - https://github.com/tc39/proposal-slice-notation/ https://github.com/tc39/proposal-slice-notation/ (and https://github.com/tc39/proposal-slice-notation/pull/32 https://github.com/tc39/proposal-slice-notation/pull/32)