Pentive VS quickjs-emscripten

> I wonder what the ecosystem would look like if things were otherwise.

Shameless plug - I'm building https://github.com/AlexErrant/Pentive which is basically GitHub/Reddit for flashcards. Very much pre-product and a WIP, though the offline client proof of concept is done.

I also enjoyed the Treesitter talk from 5 years ago by Max Brunsfeld https://www.youtube.com/watch?v=Jes3bD6P0To

I'm currently building a query language whose grammar is very much inspired by Github's search syntax. I'm using Lezer, which is a GLR like Treesitter, so this talk learned me some parser generators (I've no formal CS education). Here's my grammar, a playground, and an example search query if anyone wants to play with it

https://github.com/AlexErrant/Pentive/blob/main/app/src/quer...

https://littletools.app/lezer

    -(a) spider-man -a b -c -"(quote\\"d) str" OR "l o l" OR  a b c ((a "c") b) tag:what -deck:"x y"

Not really. There are options for sharing cards on Anki https://www.reddit.com/r/Anki/comments/14j2jfy/deck_sharing_... but their collaboration features are limited.

I myself am building an Anki clone https://github.com/AlexErrant/Pentive with collaboration built in as a first class citizen, though its far from primetime. Currently stewing on how to get the SR algorithm, FSRS, to compile to wasm.

https://github.com/AlexErrant/Pentive

A free, open source, local-first, spaced repetition system that works offline, has p2p syncing, plugins, and first class support for collaboration. It's GitHub/Reddit for flashcards.

I basically took Anki and turned it into a webapp >_>

I find Solid's model pretty damn close to "compiling down to nothing". I chose Solid for my project because I wanted to support plugins that used other UI frameworks. I recently got a Svelte plugin working with the SolidJS router. I could probably make it prettier... but it's literally a call to Solid's `createComponent` with the Router and an anchoring div to which the Svelte component is mounted. Ezpz.

https://github.com/AlexErrant/Pentive/blob/main/example-plug...

I'm also building an Anki clone (sigh) that I'm calling "Github for flashcards".

>A free, open source, local-first, spaced repetition system that works offline, has p2p syncing, plugins, and first class support for collaboration.

https://github.com/AlexErrant/Pentive

Very much a WIP, completely unusable, but I recently made a video demoing the technical proof of concept.

Anki, imo, already has an open algorithm (that the user can change via plugins), universal interfaces, and is "self-hosted". My eyes perked up at REST api, but it doesn't look like there's a centralized server that hosts shared cards, which is where my mind went.

I'm building https://github.com/AlexErrant/Pentive/ which is basically Anki + Reddit - people can optionally upload their cards for others to download, and the most popular cards rise to the top. It's FLOSS, offline-first, supports plugins and p2p syncing, and is very much a WIP. My proof of concept is almost done though, which demos the critical technologies in a secure way.

I'm using cr-sqlite right now in my Anki clone: https://github.com/AlexErrant/Pentive

It's basically an offline-first flashcard webapp. CR-Sqlite allows for incremental syncing.

With Anki (the app from which I'm taking my inspiration), syncing is _not_ incremental - basically it just copies SQLite files around. So for example, the app could be on an iPhone with cards a card `A` reviewed, but the app on an iPad could make changes to the template on which card `A` is based, and that's enough to cause a conflict - you must take changes from only the iPad or only the iPhone. (To be clear - Anki does have some incremental syncing capabilities - I'm picking an intentionally pathological example.) CR-SQLite will mean that everything is incremental, however.

Basically makes 3 way merges a breeze (or n-way merges, really).

A FLOSS, offline-first, spaced repetition system that has first class support for collaboration, curation, and plugins. It's Reddit for flashcards.

https://github.com/AlexErrant/Pentive

I've been thinking about this for a stupid amount of time... thinking that someday someone's going to improve on Anki. Finally got tired of it and said that person's me.

Based on your comment below I think you figured out the difference - but if you're looking to execute JS, you can pick between ShadowRealm (where available, or using a polyfill) or my library quickjs-emscripten.

Pros of quickjs-emscripten over ShadowRealm:

- You can use quickjs today in any browser with WASM. ShadowRealm isn't available yet, and polyfills have had security issues in the past. See https://www.figma.com/blog/an-update-on-plugin-security/

- In ShadowRealm eval, untrusted code can consume arbitrary CPU cycles. With QuickJS, you can control the CPU time used during an `eval` using an [interrupt handler] that's called periodically during the eval.

- In ShadowRealm eval, untrusted code can allocate arbitrary amounts of memory. With QuickJS, you can control both the [stack size] and the [heap size] available inside the runtime.

- quickjs-emscripten can do interesting things with custom module loaders and facades that allow synchronous code inside the runtime to call async code on the host.

Pros of ShadowRealm over QuickJS:

- ShadowRealm will (presumably?) execute code using your native runtime, probably v8, JavaScriptCore, or SpiderMonkey. Quickjs is orders of magnitude slower than JIT'd javascript performance of v8 etc. It's also slower than v8/JSC's interpreters, although not by a huge amount. See [benchmarks] from 2019.

- You can easily call and pass values to ShadowRealm imported functions. Talking to quickjs-emscripten guest code requires a lot of fiddly and manual object building.

- Overall the quickjs(-emscripten) API is verbose, and requires manual memory management of references to values inside the quickjs runtime.

[interrupt handler]: https://github.com/justjake/quickjs-emscripten/blob/main/doc...

[stack size]: https://github.com/justjake/quickjs-emscripten/blob/main/doc...

[heap size]: https://github.com/justjake/quickjs-emscripten/blob/main/doc...

[benchmarks]: https://bellard.org/quickjs/bench.html

The thing I want to achieve with WebAssembly is still proving a lot harder than I had anticipated.

I want to be able to take strings of untrusted code provided by users and execute them in a safe sandbox.

I have all sorts of things I want this for - think custom templates for a web application, custom workflow automation scripts (Zapier-style), running transformations against JSON data.

When you're dealing with untrusted code you need a really robust sandbox. WebAssembly really should be that sandbox.

I'd like to support Python, JavaScript and maybe other languages too. I want to take a user-provided string of code in one of those languages and execute that in a sandbox with a strict limit on both memory usage and time taken (so I can't be crashed by a "while True" loop). If memory or time limit are exceeded, I want to get an exception which I can catch and return an error message to the user.

I've been exploring options for this for quite a while now. The furthest I've got was running Pyodide inside of Deno: https://til.simonwillison.net/deno/pyodide-sandbox

Surprisingly I've not found a good pattern for running a JavaScript interpreter in a WASM sandbox yet. https://github.com/justjake/quickjs-emscripten looks promising but I've not found the right recipe to call it from server-side Python or Deno yet.

Can Extism help with this? I'm confident I'm not the only person who's looking for a solution here!

"Safely execute untrusted Javascript in your Javascript, and execute synchronous code that uses async functions" quickjs-emscripten, NPM

This maybe, as a start?

https://github.com/justjake/quickjs-emscripten

QuickJS Running in WebAssembly\ (17 comments)

The library was inspired by Figma’s blog posts about their plug-in system: https://github.com/justjake/quickjs-emscripten#background

If you need to call into user-generated Javascript synchronously or have greater control over the sandbox environment, you can use WebAssembly to run a Javascript interpreter: https://github.com/justjake/quickjs-emscripten#quickjs-emscr...

QuickJS in WebAssembly is much slower than your browser's native Javascript runtime, but possibly faster than async calls using postMessage. As an added bonus, it can make async functions in the host appear to be synchronous inside the sandbox using asyncify: https://emscripten.org/docs/porting/asyncify.html.

You can use One Weird Trick with generator functions to make your code "generic" over synchronicity. I use this technique to avoid needing to implement both sync and async versions of some functions in my quickjs-emscripten library.

The great part about this technique as a library author is that unlike choosing to use a Promise return type, this technique is invisible in my public API. I can write a function like `export function coolAlgorithm(getData: (request: I) => O | Promise): R | Promise`, and we get automatic performance improvement if the user's function happens to return synchronously, without mystery generator stuff showing up in the function signature.

Helper to make a function that can be either sync or async: https://github.com/justjake/quickjs-emscripten/blob/ff211447...

Uses: https://cs.github.com/justjake/quickjs-emscripten?q=yield*+l...

This seems like a pretty nice, recently enabled way of getting a sandboxed js environment: QuickJS compiled to WASM: https://github.com/justjake/quickjs-emscripten.