A fast 100% spec compliant, self-hosted JavaScript parser | Hacker News Reader

A fast 100% spec compliant, self-hosted JavaScript parser

github.com

42 pointscheanrick7 comments

Interesting project. Wonder if this would be useful for web based programs that could allow third party add-ons, etc... I was thinking WASM with some bindings would be prefect, but being in JS itself sounds cool as this acts as a sort of sandbox I'd imagined (Well I assume someone could try to make an infinite loops and lock it up?). Be neat if could some how try to limit/monitor memory and CPU usage.

The purpose of this project is to parse JavaScript (turn a flat string of code into a structured tree), not evaluate it.

> web based programs that could allow third party add-ons

The library in the current post, Seafox - cute name! - is "just" the parser, turning JavaScript code into an abstract syntax tree. One would need a sandboxed interpreter/evaluator/virtual machine to run it.

You might be aware of Figma's efforts, where they compiled Fabrice Bellard's QuickJS engine (in C) to WASM, to use for their plugin system.

https://www.figma.com/blog/how-we-built-the-figma-plugin-sys...

https://www.figma.com/blog/an-update-on-plugin-security/

https://bellard.org/quickjs/

The first article describes an earlier system using Realms, a shim/polyfill for an ECMAScript proposal.

https://github.com/agoric/realms-shim/

https://github.com/tc39/proposal-realms

These are pretty surprising claims... As far as I know, V8 itself is written in C++, is this self-hosting parser faster than Node's parser?

Fair point, though I read it like this, which doesn't make the claim _so_ bold :)

> Twice as fast as other Javascript parsers (sic) written in JavaScript.

Yes, this was my interpretation too (should probably be made more clear). Most JS dev tools are written in JS (Webpack, Babel, VSCode) so there's a large use-case for a fast JS-native parser. It could also, theoretically, be run in-browser for a macro system or something.

Is it possible to build an AST with v8 in JS?

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