arv (@arv.tools) · Mythryl

arv

@arv.tools

Partner at rocicorp.dev, building zero.rocicorp.dev Ex V8, Chrome, TC39, Gmail, Gears

120 followers 161 following56 posts

I built an implementation of the TC39 structs proposal that you can use today: `struct` and `shared struct`, Atomics.Mutex and Atomics.Condition, and objects that really are shared between workers. A compiler and a runtime, on npm as @arv/structs. structs.arv.tools

structs.arv.toolsStructs DocsThe TC39 structs proposal for JavaScript today: structs, shared structs, SharedArray, Atomics.Mutex and Atomics.Condition, with a compiler for their syntax.

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arv

@arv.tools

The playground runs your program on 1, 2, 4 and 8 workers, so you can watch it scale. The Mandelbrot demo gets about 7.7x on 8 workers in Chrome, then prints the picture. structs.arv.tools/playground/

structs.arv.toolsStructs playgroundWrite the TC39 structs proposal's struct and shared struct syntax, see the JavaScript it compiles to, and run it on Web Workers that share memory, in your browser.

arv

@arv.tools

It sticks closely to the spec, and the docs list each place it differs. npm install @arv/structs npm install -D @arv/structs-compiler Code: github.com/arv/structs

github.comGitHub - arv/structs: The TC39 structs proposal for JavaScript today: structs, shared structs, SharedArray, Atomics.Mutex and Atomics.Condition, with a compiler for their syntaxThe TC39 structs proposal for JavaScript today: structs, shared structs, SharedArray, Atomics.Mutex and Atomics.Condition, with a compiler for their syntax - arv/structs

arv

@arv.tools

structs.arv.toolsStructs DocsThe TC39 structs proposal for JavaScript today: structs, shared structs, SharedArray, Atomics.Mutex and Atomics.Condition, with a compiler for their syntax.

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arv

@arv.tools

How it works: the compiler turns struct syntax into plain JavaScript. Shared structs live in one SharedArrayBuffer heap that every worker attaches to, and each one is a Proxy over its slots in that memory.

arv

@arv.tools

With TypeScript it goes further. Where the types prove that an object is a shared struct, the compiler drops the Proxy and reads and writes the heap directly. The slower Proxy path runs only where it can't prove that.

arv

@arv.tools

structs.arv.toolsStructs DocsThe TC39 structs proposal for JavaScript today: structs, shared structs, SharedArray, Atomics.Mutex and Atomics.Condition, with a compiler for their syntax.

arv

@arv.tools

```js shared struct Counter { count = 0; lock = new Atomics.Mutex(); } ``` Pass a Counter to a worker and it gets the same object, not a copy. Take the lock with `using _ = Atomics.Mutex.lock(c.lock)` and count away.

arv

@arv.tools

Last week I gave Porffor shared-everything threads: one heap, every object shared, races allowed but never a torn value. github.com/arv/porffor/tree/arv/shared-everything-threads/threads This week, the opposite bet: @arv/threads, threads for plain TypeScript on Web Workers 🧵 threads.arv.tools

threads.arv.toolsThreads DocsThreads for JavaScript, in plain TypeScript, on Web Workers and a SharedArrayBuffer.

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arv

@arv.tools

A checker on TypeScript 7 proves the rules: no use after a move, no mutable object reaching two threads. A Vite plugin compiles shared structs down to typed-array reads and writes.

arv

@arv.tools

Try it in the browser, the TypeScript and the JS it compiles to side by side: threads.arv.tools/playground/ npm install @arv/threads. Still experimental: the compiler is a tsgo fork you build yourself, for now. Built mostly by iterating with Claude Code.

threads.arv.toolsThreads playground

arv

@arv.tools

threads.arv.toolsThreads DocsThreads for JavaScript, in plain TypeScript, on Web Workers and a SharedArrayBuffer.

arv

@arv.tools

Why the opposite? I first tried Porffor’s model in plain JS on Web Workers. Workers can’t share V8 objects, so an object had to move into shared memory as soon as a second thread could see it. It worked, but reading a shared object got ~17x slower.

arv

@arv.tools

So now every value is one of three kinds: • owned by one thread, and it moves • deeply immutable, copied once per reader • a struct or SharedArray, laid out in shared memory Ordinary code is plain JS. On 8 threads, Mandelbrot runs 7.6x faster than single-threaded JS, and N-body 4x.

arv

@arv.tools

What is happening to all the Paris meetups? There hasn't been many lately? @parisjs.org @typescript.paris @bejs.bsky.social

arv

@arv.tools

Concurrent JavaScript, it works! Over the last couple of days I (Claude) have hacked on porffor.dev to add Threads! I've added concurrency primitives as described by Filip Pizlo here: webkit.org/blog/7846/co... You can play with in your browser at porffor-threads.up.railway.app/threads/play...

webkit.orgConcurrent JavaScript: It can work!With the recent addition of SharedArrayBuffer, concurrency is finding its way into the JavaScript language.

arv

@arv.tools

This is also what Bun is prototyping at github.com/oven-sh/WebK...

github.comShared-memory threads for JavaScriptCore (experimental, not working yet) by Jarred-Sumner · Pull Request #249 · oven-sh/WebKitWhat this is Shared-memory threads for JavaScriptCore. new Thread(fn) runs fn on another thread, in the same heap, with the same objects. No structured clone, no message passing, no SharedArrayBuff...

arv

@arv.tools

TIL: Prefer `Float64Array` over `Array<number>` when you care about sorting. Sorting the former is a lot faster.

arv

@arv.tools

This might seem like it so fast that it does not matter... but... Hermes.

arv

@arv.tools

And here is the Hermes graph. Note that the actual numbers are not representative since this was run on iOS simulator on a MacBook M5. In reality old Android phones are at least 5x slower.

arv

@arv.tools

TIL: Prefer `Float64Array` over `Array<number>` when you care about sorting. Sorting the former is a lot faster.

arv

@arv.tools

@hashseed.bsky.social @ajklein.bsky.social

arv

@arv.tools

TIL: Prefer `Float64Array` over `Array<number>` when you care about sorting. Sorting the former is a lot faster.

arv

@arv.tools

Also, unfortunately `TypeArray.prototype.sort` does not use TimSort... Not sure why???

Crazy typescript

Needed some minor tweaks to allow strings too www.typescriptlang.org/play/#code/C...

typescriptlang.orgTS Playground - An online editor for exploring TypeScript and JavaScriptThe Playground lets you write TypeScript or JavaScript online in a safe and sharable way.

arv

@arv.tools

15 Sept

Testing rindle again

arv reposted

Jeremy Keith

@adactio.com

14 Sept

Journal: Stalling installing Trying to get past Webkit’s blockage at the W3C. 🔗https://adactio.com/journal/22757

arv

@arv.tools

19 Aug

I miss you Emil.

arv reposted

Rob Palmer

@robpalmer.bsky.social

10 June

Jarred Sumner experiments with multi-threaded JavaScript 🧪 Filip Pizlo's "wild thought experiment" from 2017 is brought to life 🔥 Unlike existing approaches (workers, SharedArrayBuffer) this shares the JS heap. It means threads directly access the same JS objects. github.com/oven-sh/WebK...

arv reposted

Zero

@zero.rocicorp.dev

1 May

1️⃣ 4️⃣ Zero 1.4 available * Improved query analyzer * Periodic auto reset for disaster recovery * 7x faster index creation * 2x faster backfills * Up to ~50% faster hydration * ~20 misc fixes * A cute ad for Cloud Zero No breaking changes. You should update soon. zero.rocicorp.dev/docs/release...

zero.rocicorp.devZero 1.4Performance and Reliability Improvements

arv reposted

Wojciech Maj

@wojtekmaj.pl

9 Apr

I wanted an app that would let me see my remaining Codex and GitHub Copilot usage quotas as easily as I can see my remaining battery life. Prompted Codex, went to the gym, came back to this. Nice.

arv reposted

Alex Russell

@infrequently.org

9 Apr

Amazing post. I hope web devs understand this as downstream of antitrust pressure on Apple re: iOS & other browsers. @open-web-advocacy.org won the headcount Apple poured in since '20 because it allowed them to claim engagement w/o threatening the app store: blog.gitbutler.com/the-great-cs...

blog.gitbutler.comThe Great CSS ExpansionCSS now does what Floating UI, GSAP ScrollTrigger, Framer Motion, and react-select used to require JavaScript for. Here is exactly how much that saves, why these libraries were painful beyond their size, and what the platform still hasn't figured out.

arv reposted

Stefan Judis

@stefanjudis.com

7 Apr

A nine-year-old CSS spec issue has been resolved! 🎉 `position: sticky` now tracks the nearest scrolling container per axis. Want to stick an element to a scroll container AND the document? Soon possible. Chromium only for now, but great to see this land! https://www.bram.us/2026...

arv reposted

Stefan Judis

@stefanjudis.com

4 Apr

This is absolutely beautiful and very well done. > Nothing you own is finished. Everything exists in a state of permanent incompletion, permanently needing. https://www.terrygodier....

arv

@arv.tools

2 Apr

This RegExp is O(1) if the string is `SeqOneByteString` 🎉 ```js const isOneByte = !/[^\x00-\xff]/.test(str); ```

arv

@arv.tools

2 Apr

However, if the string is a `SeqTwoByteString` and large it has to do a linear scan which of course is not so fast. Anyone have any tricks up their sleeves to detect if a string is a a two byte string in O(1)?

arv

@arv.tools

25 Mar

We're officially one dot oh now 🎉

Aaron Boodman@aaronboodman.com

Zero to 1.0 After two years of work, 50+ releases, thousands of commits, and hundreds of bugfixes, we are officially declaring Zero stable and ready for production workloads. zero.rocicorp.dev/docs/release...

zero.rocicorp.devZero 1.0First Stable Release

arv reposted

Aaron Boodman

@aaronboodman.com

25 Mar

zero.rocicorp.devZero 1.0First Stable Release

arv

@arv.tools

22 Mar

@diabrowser.com bsky.app/profile/orpa... Opensearch please.

Banda Bassotti@orpach.neocities.org

Opensearch is such a good feature, it's a shame nothing besides firefox supports it anymore. (you can right-click on the URL bar to easily add it on npmx.dev) In chrom*, they expect you to use an extension per search engine or manually add the replacement string in the settings window.

arv

@arv.tools

20 Mar

@vite.dev 8 I need to figure this one out...

arv reposted

Younes Jaaidi

@younesjd.dev

17 Mar

Debounces, delays, intervals... they either break your tests or slow them down. ⏩ Since @vitest.dev 4.1.0, you can now "fast-forward" time in your tests with `nextTimerAsync` tick mode. ❤️ credit goes to Andrew Scott (@angular.dev team) 🧑‍🍳 recipe → cookbook.marmicode.io/angular/test...

I voted 🇫🇷🗽

I really like where @remix.run is going in v3. So much less magic and using the platform for its strength. Disclaimer: I designed and implemented ES6, custom elements, shadow dom, some "modern" dom apis (classList, template element, append, remove...), making EventTarget concrete etc...

I'm really sold on fine grained reactivity - all the way from your database (zero.rocicorp.dev) to your UI (zero.rocicorp.dev/docs/solidjs)

zero.rocicorp.devZero DocsThe official documentation for Zero by Rocicorp.

❤️

Another master piece by @nolanlawson.com nolanlawson.com/2026/02/18/y... The passion of becoming a programmer really resonates with me. Thank you Nolan.

nolanlawson.comYou had a storyYou had a story you used to tell yourself about how you got here in life. You’d share the story with others. Maybe you’d be at a party, and someone would ask what you do, and you’…

arv reposted

{🧪} +paoloricciuti.svelte

@paolo.ricciuti.me

22 Jan

Man customizable select is sooo cool! Modern CSS is another level of powerful. svelte.dev/playground/8...

One thing that I'm a bit unclear on at this point is `update`. Based on the presentation all it did was rerender but what does it mean to rerender? What about DOM state (selection, scroll position)? What about JS state?

I'm also intrigued by the higher level events they designed. It looks really nice. We did this in Closure Library but we didn't get it right and in the end it wasn't used much. Here is our "action" event. github.com/google/closu...

4 years ago today you passed away. I wish I could turn back time and come and rescue you.

arv reposted

Local-First Conf

@localfirstconf.com

27 May 2025

ZVM - Zero View Management @aaronboodman.com introduced the incredible tech that enables the zerosync.dev sync engine to almost instantaneously update realtime queries.

arv reposted

Angelos Arnis 🏴

@arn.is

30 Apr 2025

A story in two parts

arv reposted

George Takei

@georgetakei.bsky.social

17 Mar 2025

I know this first hand. When I was a child, my entire community was branded as spies and sabateurs, justifying our internment inside barbed wire camps for years without due process, trial or charge.