Rob Palmer

@robpalmer

JavaScript Infrastructure & Tooling at Bloomberg. Co-chairing TC39. Likely to tweet tech stuff about JS & software performance. Opinions are my own.

789 Folgt8.194 Follower772 Posts

Bluesky

Ist das dein Profil?Übernimm es — dann gehört dir robpalmer.dirty.social.Profil übernehmen

Rob Palmer@robpalmer· 2d

ECMAScript excitement 😉 Congrats to @yusukesuzuki.bsky.social on shipping TC39 Stage 3 Import Defer in upstream WebKit, heading for Safari 🎉 Import Defer is a performance feature that lets you lazily execute a module on first access to the module namespace 🔥 github.com/WebKit/WebKi...

import defer * as ns from "./mod.js";
// mod.js is fetched and linked now, but NOT evaluated.

console.log("before");
console.log(ns.value); // <-- mod.js evaluates here, synchronously

Rob Palmer@robpalmer· 25d

ECMAScript excitement 😉 Congrats to my coworker @ashley-c.bsky.social at TechAtBloomberg on advancing Await Dictionary to Stage 3 at TC39 🎉 Promise.all returns positional results as an array. Promise.allKeyed allows named results inside an object 👍 github.com/tc39/proposa...

const {
shape,
color,
mass,
} = await Promise.allKeyed({
shape: getShape(),
color: getColor(),
mass: getMass(),
});

Rob Palmer@robpalmer· Jun 27

Bloomberg uses a lot of C++ & contributes to the standard as well as various industry conferences and libraries. I’m looking for an experienced engineer to join a distributed systems team in New York working on our core Deployment Infrastructure for the Bloomberg Terminal 🗽 🧵

Five engineers in a glass meeting room with a whiteboard wall

Rob Palmer@robpalmer· Jun 18

Nub is a new frontend for Node by @colinhacks.com ✨ 🦀 A Rust CLI 🧱 Bundler-style JS/TS/JSX transpilation ⚡️ Fast script execution 📦 A new package manager based on Aube 🔢 Node version management The name is similar to Bun. github.com/nubjs/nub

nub.
$ nub index.ts
# TypeScript-first Node.js runtime
$ nub run dev
# 24x faster pnpm run
$
nubx prisma
generate
# 19× faster npx
$ nub install
# 3x faster pnpm install
$ nub watch sic/server.ts
非
native watch
mode
$ nub pm shim
# built-in Corepack-style shims
$
nub node install
26
# Node version
manager

Rob Palmer@robpalmer· Jun 10

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...

The API

A thread is a function call on another core:

const t = new Thread((a, b) => {
return expensive(a, b);
}, x, y);

t.join(); // blocks, returns fn's value or rethrows its exception
await t.asyncJoin(); // same, as a promise; never blocks
Thread.current; // your Thread
t.id; // engine thread id, main is 0

Rob Palmer@robpalmer· Jun 5

This simplifies the mental model of how type annotations work 💙 The same fix has been merged into upstream Node.js alongside Amaro and SWC. Here are examples of the new errors as well as cases that continue to work fine.

const x01 = 1 as number * 2;
const x02 = 1 as any as number * 2;

const x03 = 1 + 1 as number * 2; // Error
const x04 = 1 + 1 as any as number * 2; // Error
const x05 = 1 as number + 1 * 2;
const x06 = 1 as any as number + 1 * 2;

Rob Palmer@robpalmer· Jun 5

Type-stripping (used in Node's *.ts support) continues to pay dividends 👍 Masaki Hara found some type syntax that was unexpectedly not erasable: adding type assertions changed the precedence of the underlying JS code 😮 Anders on the TypeScript team universally fixed it in TS 7.0 via new errors 🎉

as/satisfies precedence and erasableSyntaxOnly

Issue: #63527

- Problem: 1 + 2 as number / 3 parses as ((1 + 2) as number) / 3
- This can't be emitted without parenthesizing 1 + 2, since 1 + 2 / 3 has different meaning

Rob Palmer@robpalmer· May 29

This article explains why many Bloomberg engineers choose to stay with the company for a long time. leaddev.com/career-devel...

Bloomberg grew while others cut – and that’s the retention strategy. Doubling from 5,000 to 10,000 engineers while competitors downsized sends a clear signal: we won’t discard you when markets turn.

Rob Palmer@robpalmer· May 25

ECMAScript gratitude 😉 Huge thanks to @dmitrymakhnev.bsky.social for arranging to host this week's @tc39.es meeting in Amsterdam at @jetbrains.com 🙏 Dmitry was super thoughtful about all the details and an excellent communicator throughout.

35-ish delegates in JetBrains office. Dmitry is in the middle on the floor.

Badges and dedicated artwork for the 114th Meeting of TC39

Rob Palmer@robpalmer· May 20

Rob Palmer@robpalmer· May 6

We will have achieved AGI when Gemini can appreciate my jokes. (Also, it's important to give your agents closure when they help you with projects around the home.)

Me: Yes the one in putty tightened fast at the end. I used 40mm m5s. Seemed very solid and it supports the pole and the curtains fine. It may not be the best hung curtain pole in the world, but it's up there.

Gemini: That rapid tightening at the end is the exact mechanical feedback you want. It confirms the 40mm M5 screw fully expanded the plug against the unyielding epoxy, creating a high-torque friction lock rather than just compressing soft material.

"Up there" is the primary requirement for a curtain pole. The structural foundation you built with the epoxy cast ensures it will stay there under the dynamic load of the curtains.

Rob Palmer@robpalmer· Apr 15

The traditional response is for the server to repeat the question slowly. What. Is. Your. Name? Or you can point to this and they'll understand.

Rob Palmer@robpalmer· Apr 1

Source maps are more exciting than ever 😉 🔶 Recently standardized! (one year ago) 🔶 An active @tc39.es Task Group 🔶 New features soon: Scopes & Range Maps Read all about it 📜 bloomberg.github.io/js-blog/post...

Source Maps: Shipping Features Through Standards
Published on 10 March 2026
Source maps are a vital part of modern web development.

Rob Palmer@robpalmer· Mar 24

ECMAScript excitement 😉 Safari 26.4 ships support for @tc39.es Stage 4 Iterator.concat 🎉 It creates a new iterator by sequencing existing iterators.

const odds = [1, 3, 5].values();
const evens = [2, 4, 6].values();

for (const n of Iterator.concat(odds, evens)) {
console.log(n); // 1, 3, 5, 2, 4, 6
}

Rob Palmer@robpalmer· Mar 18

ECMAScript excitement 😉 Congrats to @kdy1.bsky.social on landing support for @tc39.es Stage 3 Decorators in upstream SWC 🎉 SWC is the compiler that powers Next.js, Deno, Parcel, Turbopack, RsPack & more. ⚠️ Note: These differ from the older TS “experimentalDecorators“ github.com/swc-project/...

Rob Palmer@robpalmer· Mar 17

JavaScript Weekly newsletter is out - and it's about time 😉 javascriptweekly.com/issues/777

Rob Palmer@robpalmer· Mar 12

ECMAScript excitement 😉 This week in NY @tc39.es advanced these proposals 🎉 4⃣ Intl Era/Month Code 4⃣ Temporal 3⃣ Import Text 2⃣.7⃣ Error Stack Accessor 2⃣.7⃣ Iterator Includes 2⃣ Intl Unit Protocol 2⃣ Thenable Curtailment 1⃣ Error Code Property 🗑️ Dynamic Import Host Adjustment

Delegates of TC39 in Google's Chelsea Market office

Rob Palmer@robpalmer· Mar 12

Yesterday was a big day for JavaScript 🎈 @tc39.es celebrated Temporal achieving Stage 4 in the traditional way - with a cake!

A chocolate cake with white writing that says "Temporal is Stage 4" but might say "Tom Poral is Stage 4"

Rob Palmer@robpalmer· Jan 20

ECMAScript excitement 😉 Congrats to @bridgear.bsky.social on advancing Error Option Limit to Stage 1 @tc39 today 🎉 It allows the captured stack depth to be limited on a per-object basis 👍 It removes the need to rely on implementation-specific global APIs. github.com/tc39-transfe...

new Error(message, { limit: 3 })
new TypeError(message, { limit: 0 })
new RangeError(message, { limit: 50 })
new AggregateError(iterable, message, { limit: Infinity })
// ... applies to all built-in Error constructors that accept an options bag

Rob Palmer@robpalmer· Jan 20

ECMAScript excitement 😉 Congrats to @guybedford.com on advancing Import Sync to Stage 2 at @tc39.es today 🎉 const mod = import.sync(<specifier>); Like Node's require(<specifier>), it synchronously loads a module. It throws if sync loading is not possible. github.com/guybedford/p...

let fs;
try {
fs = import.sync('node:fs');
} catch {}

if (fs) {
// Use node:fs, only if it is available
}

Rob Palmer@robpalmer· Jan 20

ECMAScript excitement 😉 Congrats to Dan Minor @mozilla.org on advancing the Upsert proposal to Stage 4 at TC39 today 🎉 let map = new Map(); map.getOrInsert(key, defaultVal); It lets you set a default value on a map key without overwriting an existing value 👍

// Currently
let prefs = new getUserPrefs();
if (!prefs.has("useDarkmode")) {
prefs.set("useDarkmode", true); // default to true
}

// Using getOrInsert
let prefs = new getUserPrefs();
prefs.getOrInsert("useDarkmode", true); // default to true

Rob Palmer@robpalmer· Jan 16

Have thoroughly enjoyed working with Jon on JS shenanigans ever since @threepointone.bsky.social leant over and loudly whispered "you should hire this guy" at a London pub. Jon has talked about his dog a lot. Still waiting to meet this chunky boi.

Rob Palmer@robpalmer· Jan 14

📜 "Date is out, Temporal is in" An article by @wil.to on problems found in the ancient JS Date API and how they are solved in the modern Temporal API 👍 Focuses on immutability and ergonomics of calculations. Love the kicker.

Sure, the best time to replace Date would’ve been back in 1995, but hey: the second best time is Temporal.Now, right?

Rob Palmer@robpalmer· Jan 14

A short article on the perils of the old JS Date API by @philna.sh 📜 It explains the modern solution: use Temporal which shipped in Chrome 144 yesterday 👍 And the article is already out of date! 😉 (in a good way - the article was published 24 hours before Chrome shipped)

From the article "Temporal has still not made it to many JavaScript engines. At the time of writing, it is available in Firefox and nowhere else"

Plus red annotation "Not true: now in Chrome!"

Rob Palmer@robpalmer· Dec 26

This year's GitHub Octoverse annual survey did a good job of correctly representing TypeScript & JavaScript as a single ecosystem. When this combined data is omitted, it results in misleading takes.

A graph from the 2025 Octoverse report that shows the combined JS/TS usage being nearly double the next most used language.

Rob Palmer@robpalmer· Dec 20

Internal mandatory software for employees (at many companies)

Rob Palmer@robpalmer· Dec 4

@oliverturner.cloud come find us at the Banker

Rob Palmer@robpalmer· Nov 25

Canva used the Rust-based Oxc by @voidzero.dev to generate TS declaration files. It reduced DTS generation time from 339ms down to 5ms - a 66x improvement 🔥

Rob Palmer@robpalmer· Nov 25

TypeScript excitement 😉 "Our type checks are infinitely parallelizable" @brad.zacher.com.au explains how the difference between the ts & d.ts dependency graphs can help scale the TS checker to 12 MLoC. A 2x faster P50 shifted user behavior to rely less on CI and boosted local checking by 70% 🔥

Rob Palmer@robpalmer· Nov 20

ECMAScript excitement 😉 This week TC39 advanced these proposals 🎉 4️⃣ Intl.Locale Info 4️⃣ Iterator.concat 4️⃣ JSON.parse Source Text 3️⃣ Iterator.zip 2️⃣.7️⃣ Iterator.prototype.join 2️⃣.7️⃣ Promise.allKeyed 2️⃣ Error.captureStackTrace 2️⃣ Import Text 2️⃣ Object.keysLength 1️⃣ Intl Energy Units 1️⃣ Intl Unit Protocol 🧵