Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

What’s New in ES2019

blog.tildeloop.com

Post reply on HN
Print view View original

141–150 of 411 posts

Re: What’s New in ES2019

#141

Post by acdha »

mmartinson wrote: post #101

Honest question, not meant to be inflammatory. If we still need to target es5 4 years later, and transpilation is standard practice, why bother? Is the evolution of JS not directed in practice by the authors of Babel and Typescript? If no one can confidently ship this stuff for years after, what’s the incentive to even bother thinking about what is official vs a Babel supported proposal. I like the idea of idiomatic…

> If we still need to target es5 4 years later, and transpilation is standard practice, why bother?

Your “we” isn’t everyone else’s. Some places need to support very old browsers but even in places like that usually not every app does. Those people are pushing the state of the art forward since they do real work outside of the standards process and that provides useful feedback to both the standards committees and browser developers.

Re: What’s New in ES2019

#142

Post by masklinn »

dspillett wrote: post #102
john-foley wrote: post #23

Hard to believe that const arr4 = [1, 2, , 4, 5]; is valid.

Seems perfectly logical to me: an array of length 5 with four populated elements and one empty one (3). Though I did double-check my understanding that the length property would report 5 rather than 4 (it does). What looks out of place to you in that example? Would it make more sense to you with a very slightly less arbitrary example, perhaps arr = ['Value for 0', 'Value for 1', , 'Value for 3', 'Value for 4']; inste…

> What looks out of place to you in that example?

Most languages don't have sparse arrays so it's really weird.

> Would it make more sense to you with a very slightly less arbitrary example, perhaps arr = ['Value for 0', 'Value for 1', , 'Value for 3', 'Value for 4']; instead of simple mapping ints to ints?

You'd usually put an explicit `null` there, especially as HOFs skip "empty" array cells so

    ['Value for 0', 'Value for 1', , 'Value for 3', 'Value for 4'].map(_=>1)
returns

    [1, 1, , 1, 1]
which is rarely expected or desirable.

Re: What’s New in ES2019

#143

Post by [deleted] »

MH15 wrote: post #104
dsego wrote: post #99

Earlier quoted context omitted.

Honest question, not playing. What is exactly exciting about it? 2020 is around the corner and the language created back in 1995 is only now getting features that have been standard in many other languages, either as part of the core language or the standard library for decades.

It's exciting to see the language that we use for the web gain these features (albeit late)! These changes will allow us to follow better programming practices with less overhead.

[deleted]

Re: What’s New in ES2019

#144

Post by snek »

ojosilva wrote: post #138

A year back I dropped a proposal idea at the EcmaScript discussion list, I hope it get's picked up sometime. My idea is that `let`, `var` and `const` return the value(s) being assigned. Basically I miss being able to declare variables in the assertion part of `if` blocks that are scoped only during the `if()` block existence (including `else` blocks). Something along these lines: if( let row = await db.findOne() ) {…

This has been discussed a few times on IRC, but no one has made a proposal yet afaik.

Re: What’s New in ES2019

#145

Post by ShinTakuya »

iraldir wrote: post #18
kuon wrote: post #6

The part about parameter less catch reveals a lot about the philosophy of the language. For me, silencing error like this is a bad practice. You may still produce a sane error in the catch, but the design goes toward silencing things. I really love languages that force you to handle errors up to the top level.

It does, though I wouldn't go to the same conclusion. It gives more freedom to the developer. They are lot of cases where errors are in fact, expected. Parsing a user inputted JSON. Making a request to check internet connection availability. Any promise that is going to be consumed by an async - await pattern. In those cases (and many more), you may want to try something just simply to see if it works. It's completel…

The problem is that the catch block will catch all errors, so if a different type of error to the one you expected occurs then it gets silently swallowed. This is the equivalent of catching the generic Exception class in python. Horrendous terrible practice in anything but the hackiest scripts.

Re: What’s New in ES2019

#146

Post by speeder »

simias wrote: post #139
mmartinson wrote: post #101

Honest question, not meant to be inflammatory. If we still need to target es5 4 years later, and transpilation is standard practice, why bother? Is the evolution of JS not directed in practice by the authors of Babel and Typescript? If no one can confidently ship this stuff for years after, what’s the incentive to even bother thinking about what is official vs a Babel supported proposal. I like the idea of idiomatic…

That's not unique to JS. Some compilers took over a decade to implement C99 features. Most of us C coders were still defaulting to C89 for portability well into the late 00's. But now C99 is mainstream enough that you can (mostly) safely target it. If you never release new standards you'll never be able to use them. I realize that in JS world 4 years is basically an eternity so it's hard to project that far but I'm s…

Sadly the "mostly" is because threads :(

It is the part I was most excited about C99 and was very disappointed that it is so poorly supported.

Re: What’s New in ES2019

#147

Post by Ajedi32 »

Dextro wrote: post #11
afandian wrote: post #3

It's great to see JS getting some of the features of better planned languages. But I'm still very nervous about some of the stuff mentioned here with regard to mutation. Taking Rust and Clojure as references, you always know for sure whether or not a call to e.g. `flat` will result in a mutation. In JS, because of past experience, I'd never be completely confident that I wasn't mutating something by mistake. I don't…

Yes, this is a real problem and I've been bitten by it more times than I can count. Now I always keep this handy website ready: https://doesitmutate.xyz/

For what it's worth, there are only two, maybe three methods in that entire list that mutate where it's not obvious: sort, reverse, and (maybe) splice. All the other methods (like push, pop, fill, etc) are methods whose entire purpose is to mutate the array.

Re: What’s New in ES2019

#148

Post by cocoflunchy »

ojosilva wrote: post #138

A year back I dropped a proposal idea at the EcmaScript discussion list, I hope it get's picked up sometime. My idea is that `let`, `var` and `const` return the value(s) being assigned. Basically I miss being able to declare variables in the assertion part of `if` blocks that are scoped only during the `if()` block existence (including `else` blocks). Something along these lines: if( let row = await db.findOne() ) {…

Also see assignment expressions recently adopted in python 3.8: https://www.python.org/dev/peps/pep-0572/

Re: What’s New in ES2019

#149

Post by qudat »

mmartinson wrote: post #101

Honest question, not meant to be inflammatory. If we still need to target es5 4 years later, and transpilation is standard practice, why bother? Is the evolution of JS not directed in practice by the authors of Babel and Typescript? If no one can confidently ship this stuff for years after, what’s the incentive to even bother thinking about what is official vs a Babel supported proposal. I like the idea of idiomatic…

From my perspective, it is less about what we can use in the browser without transpilation, but where the js ecosystem is heading. I personally only want to write JS that is in spec because in 5 years something like decorators might not be a thing. Basically when I'm figuring out what language features I care about, I'm thinking about how hard it will be for other engineers to work on the codebase. Things that are not in spec are going to be less familiar and more time to learn. I think there's a lot of momentum with the spec and something to point to where can say "you should learn this syntax/feature because it's in the spec."

Re: What’s New in ES2019

#150

Post by qudat »

simias wrote: post #139
mmartinson wrote: post #101

Honest question, not meant to be inflammatory. If we still need to target es5 4 years later, and transpilation is standard practice, why bother? Is the evolution of JS not directed in practice by the authors of Babel and Typescript? If no one can confidently ship this stuff for years after, what’s the incentive to even bother thinking about what is official vs a Babel supported proposal. I like the idea of idiomatic…

That's not unique to JS. Some compilers took over a decade to implement C99 features. Most of us C coders were still defaulting to C89 for portability well into the late 00's. But now C99 is mainstream enough that you can (mostly) safely target it. If you never release new standards you'll never be able to use them. I realize that in JS world 4 years is basically an eternity so it's hard to project that far but I'm s…

> Regarding transpilation surely it's not as standard as you make it out to be? It's popular to be sure but handwritten javascript is not that rare nowadays, is it?

If you are building a modern web "app", not a one off set of web pages, then yes, it is the standard. It would be very weird to not see a compile (transpilation) step.

Post reply on HN