Emacs crashes when writting JavaScript

[Jackson Ray Hamilton <jackson@jacksonrayhamilton.com>]

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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


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