luajit VS reactor

> No offence, but have you written any compilers or interpreters?

I have, but nothing sophisticated.

> The points that you discuss [...] may be performance concerns for application developers [...] but they have very little to do with the optimisations you can make as a compiler/interpreter writer. [...] The only one that's somewhat relevant is 'global scope by default'

I didn't mean to imply that these where the three common traits that make both Javascript and Lua particularly hard to optimize, I just picked them as examples for how Javascript and Lua are closer to each other than most other dynamic languages.

But let's dig in a bit on your claim that things like all numbers being doubles or having a array cum map cum record type has very little to do with the optimizations you can make as a compiler/interpreter writer, because it sure seems to me that LuaJIT and V8 do a bunch of optimizations around these things. Both have dual number representations under the hood and will try to avoid representing numbers that remain in the domain of 32 bit integers as double values internally when that gives performance gains. The logic for figuring out if that's the case doesn't seem to be super-straightforward or target architecture independent from looking at the comments in <https://github.com/LuaDist/luajit/blob/master/src/lj_opt_nar...>.

LuaJIT furthermore uses NaN tagging (as do some JS engines, although not V8), which looks less attractive to me as a representation strategy if your numbers are not all/mostly notional doubles (as is indeed the case in newer version of Lua where 64bit integers are the dominant number type)

Also, as far as the super-flexible lua tables are concerned, I'm pretty sure LuaJIT goes through some amount of trouble to specialize various common use cases of tables, e.g. as arrays without holes, and surprise, so does V8 (https://v8.dev/blog/fast-properties#elements-or-array-indexe...). I don't think you'd find something equivalent in a high performance scheme implementation.

> but this doesn't touch the surface of the issues that make JS hard to optimise, such as the fact that your, say, memoisation of an object property or method may be broken by an `eval` call of an arbitrary runtime value somewhere else in the code (which, due to asynchronicity, could take place at more or less any time from the point of view of your given 'peephole').

Eval belongs to a core set of features that basically all popular dynamic languages share that presents headaches for high performance implementations. How is Javascript's eval particularly problematic in this regard, and specifically much more so than Lua's loadstring/load?

More generally what do you think makes (pre-ES6) javascript significantly harder to optimize than lua 5.0?

I'd love to see this approach make more headway in the Django community. Based on the last DjangoCon it seems like the community is coalescing around HTMX.

This tool does play very nicely with Django's templating engine; you can just have HTMX re-render a particular template block on the server, and send down that updated block. The migration path is quite clean; you just wrap your "HTMX-updated" template block in a `hx-post` div.

Having not gone too deep on HTMX, I'm interested in folks' thoughts on where it's lacking vs. LiveView and Hotwire. One area I can see is performance; Elixir is going to be faster than Django, and so if you're trying to handle high session counts over websockets. But the impression I get is that HTMX is a bit more light-weight, so I'm wondering if there's usecases that can't be met with it vs. LiveView.

Other Django libraries that haven't quite seen as much uptake:

We have https://github.com/edelvalle/reactor, and a port of Hotwire: https://github.com/hotwire-django but both of these don't seem to have much adoption (yet!).

Thank you for posting those, I wanted to post them but I don't comment often (). Wanted to chip in another contemporary: edelvalle/reactor, which is inspired by LiveView[0].

[0]: https://github.com/edelvalle/reactor

I am using Hotwire for a project, and I'm learning Elixir and Phoenix on the side. Finding edelvalle/reactor was immediately helpful to me though, because I cut my teeth on Python/Django, so reading a Python reference implementation helps me learn nuts and bolts of libraries, faster. (so, I figure that this might help someone else grok how these approaches work.)

If this sounds like a barebones version of notable frameworks like Elixir's Phoenix LiveView, Rails's StimulusReflex or Hotwire Turbo, PHP's LiveWire, Django's Reactor... well, you're right! (Bonus: my colleague @jgaskins built a LiveView clone for Crystal)

Reactor

Reactor is a LiveView library for Django. It enables you to do something similar to Phoenix LiveView using Django Channels.

It looks a bit similar to Elixir Live View. Or similar in Django https://github.com/edelvalle/reactor, there are a couple of libraries.

Django does: https://github.com/edelvalle/reactor