what kind of problem is this fat arrow feature trying to solve ?

Peter van der Zee ecma at qfox.nl
Wed Oct 2 07:11:51 PDT 2013


(In all fairness, Andrea was merely, and quite explicitly so, asking for
the rationale behind the fat arrow, not a scrutiny of his examples. Tab's
sarcastic response was unnecessary on a whole different level, too.)


On Wed, Oct 2, 2013 at 1:14 PM, Benjamin (Inglor) Gruenbaum <
inglor at gmail.com> wrote:

> There are two things here:
>
>  - In JS I (as well as most code in libraries I read) tend to use function
> expressions a lot. The arrow notation is easier to read in my opinion. It's
> shorter and more concise. That's a weak argument for it, but I think just
> making the language more concise is an argument on its own.
>
>  - While we're making function expressions shorter, let's fix `this`
> function expresisons. Pretty much every host environment be it node, the
> web browser or embedding uses deferred execution and event loop driven
> concurrency at some level.
>
> While there is nothing in JavaScript itself that dictates this sort of
> concurrency in practice events are used extensively when coding JavaScript.
> Using an object and adding handlers that need a reference to that object is
> very common in the browser and in node.
>
> It's very common in practice and having lexical this in arrow functions
> seems very useful. An indicator might be that in languages that support it
> like CoffeeScript you see it used all the time, and the fact you see people
> using the `this=that/self/_this` ""pattern"" all the time. That pattern
> introduces its own set of problems - for example it creates a closure scope
> where one might not be needed and it's boilerplate.
>
> Having fat arrow lets us solve that.
>
> Benjamin Gruenbaum
>
> ---------- Forwarded message ----------
> From: Andrea Giammarchi <andrea.giammarchi at gmail.com>
> To: "Tab Atkins Jr." <jackalmage at gmail.com>
> Cc: "es-discuss at mozilla.org" <es-discuss at mozilla.org>
> Date: Tue, 1 Oct 2013 19:35:28 -0700
> Subject: Re: what kind of problem is this fat arrow feature trying to
> solve ?
> setTimeout accept extra arguments ... I write JavaScript that uses this
> feature.
>
> `setTimeout(callback, delay, arg1, arg2, argN, evenAnObject);`
>
> so fat arrow does not solve much here, I can use self as first argument
> and I am good.
>
> `forEach` and all other arrays accept a second argument
>
> `array.forEach(doStuff, boundContextObject);`
>
> so fat arrow does not solve a thing in mostly all Array extras.
>
> for **DOM** I use handlers as specified by **W3C** so that `{handleEvent:
> function () {this}}` works better than any mess I could create with
> callbacks that I won't be unable to remove later on (as I've said) ... so I
> can use `removeEventListener(this)` in every method handled by that object.
>
> So I actually wonder what kind of JavaScript **you** write because this
> was a honest question but probably ... people not familiar with JS are the
> answer: since developers ignore part of JS specs available since every then
> we need a fat arrow to break old syntax to make the creation of self bound
> function easier.
>
> This would be already an answer so thanks for participating.
>
> br
>
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