El domingo 22 de septiembre del 2019 a las 1850 horas, Jackson Ray Hamilton escribió:

> Hola Jorge,
>
> Emacs’ JSX support is relatively new and could probably be optimized
> to perform better at scale.  I noticed similar slowdowns with files
> containing 300+ lines of JSX.
>
> Before I contributed the JSX support code to Emacs, I used
> (elp-instrument-package "js-") and (elp-results) to identify choke
> points during editing.  I felt like I was able to slightly improve
> performance for large files, going from “unusable” to merely
> “frustrating.”
>
> If you are familiar with Emacs Lisp and feel compelled to make things
> stabler and faster, perhaps you can find some time to benchmark and
> experiment in lisp/progmodes/js.el.  Otherwise, please open a bug report.
>
> Some tips if you decide to help: you mentioned an AST, but there isn’t
> one.  Parsing starts in js-syntax-propertize.  Years ago, Sebastian
> Wiesner wrote some blog articles explaining how syntax highlighting
> worked in Emacs, but he’s since removed those posts from his blog and
> they aren’t available on Internet Archive. Maybe he will provide you
> with the articles if you ask him for:
>
>  * 2014, Mar 11 Overview of Emacs Font Locking
>  * 2014, Mar 12 Syntactic fontification in Emacs
>  * 2014, Mar 26 Search-based fontification with keywords
>  * 2014, Jun 16 Advanced syntactic fontification
>
> Also, maybe you could separate your JSX code into smaller modules.
> That will make it easier for tools like Emacs, prettifiers, and
> linters to process your code.  Even though the code can probably be
> optimized, since we care about accuracy parsing time will ultimately
> be gated by file length regardless. Smaller modules are also
> consistent with some programmers’ expectations for high quality code;
> they are more likely to be below length thresholds permitting easy
> comprehension.
>
> Jackson

Hey, Jackson!

Thanks for the pointers, I'm absolutely interested in making the JavaScript (and JSX) support in
Emacs better.