Daniel Rosenwasser
@danr.bsky.social
TypeScript Product Manager and TC39 rep working on JavaScript standards.
Enthusiast of compilers, dev tools, language VMs/runtimes.
Enthusiast of compilers, dev tools, language VMs/runtimes.
Reposted by Daniel Rosenwasser
🥳 TypeSlayer is out! celebrate by posting what your type graph looks like! it legit has an actual leaderboard now: so bonus points if you win lol 🏆🏆
run: `npx typeslayer`
source: github.com/dimitropoulo...
run: `npx typeslayer`
source: github.com/dimitropoulo...
January 2, 2026 at 2:00 AM
🥳 TypeSlayer is out! celebrate by posting what your type graph looks like! it legit has an actual leaderboard now: so bonus points if you win lol 🏆🏆
run: `npx typeslayer`
source: github.com/dimitropoulo...
run: `npx typeslayer`
source: github.com/dimitropoulo...
Reposted by Daniel Rosenwasser
Your TypeScript year in review
You "silenced" 417 errors with `as any` that turned into runtime errors as soon as the code ran
TypeScript printed 4,693 error messages. 26 of them made sense
You spent 98 minutes waiting for tsc to run. During this time you spent 544 minutes reading social media
You "silenced" 417 errors with `as any` that turned into runtime errors as soon as the code ran
TypeScript printed 4,693 error messages. 26 of them made sense
You spent 98 minutes waiting for tsc to run. During this time you spent 544 minutes reading social media
December 30, 2025 at 1:59 AM
Your TypeScript year in review
You "silenced" 417 errors with `as any` that turned into runtime errors as soon as the code ran
TypeScript printed 4,693 error messages. 26 of them made sense
You spent 98 minutes waiting for tsc to run. During this time you spent 544 minutes reading social media
You "silenced" 417 errors with `as any` that turned into runtime errors as soon as the code ran
TypeScript printed 4,693 error messages. 26 of them made sense
You spent 98 minutes waiting for tsc to run. During this time you spent 544 minutes reading social media
Reposted by Daniel Rosenwasser
👋 Hi! For those unfamiliar I'm Hawk, a UX Engineer on the @vscode.dev team. As 2025 comes to a close, I've been wanting to get a pulse on how folks are writing code.
Genuinely curious: What tool(s) do you use? What do you like/dislike about them? What do you wish your tool could do that it doesn't?
Genuinely curious: What tool(s) do you use? What do you like/dislike about them? What do you wish your tool could do that it doesn't?
December 28, 2025 at 3:43 AM
👋 Hi! For those unfamiliar I'm Hawk, a UX Engineer on the @vscode.dev team. As 2025 comes to a close, I've been wanting to get a pulse on how folks are writing code.
Genuinely curious: What tool(s) do you use? What do you like/dislike about them? What do you wish your tool could do that it doesn't?
Genuinely curious: What tool(s) do you use? What do you like/dislike about them? What do you wish your tool could do that it doesn't?
Reposted by Daniel Rosenwasser
My regular PSA that if you enjoy working on developer tools, then Jane Street is kind of an amazing place. Apply here! There's no special posting, so just apply for the Software Engineering role, and express your interests in dev-tools in a note.
janestreet.com/apply
janestreet.com/apply
December 18, 2025 at 5:31 PM
My regular PSA that if you enjoy working on developer tools, then Jane Street is kind of an amazing place. Apply here! There's no special posting, so just apply for the Software Engineering role, and express your interests in dev-tools in a note.
janestreet.com/apply
janestreet.com/apply
Reposted by Daniel Rosenwasser
TypeScript excitement 😉
The infamous Dimitri is cooking up a slick type analysis tool called TypeSlayer 🔥
"If you have a large enough project, there are performance problems where you can shave 100 seconds off CI by making a 5 line change. The problem is knowing out where to make that change."
The infamous Dimitri is cooking up a slick type analysis tool called TypeSlayer 🔥
"If you have a large enough project, there are performance problems where you can shave 100 seconds off CI by making a 5 line change. The problem is knowing out where to make that change."
⚔️introducing TypeSlayer⚔️ A #typescript type performance benchmarking and analysis tool. A summation of everything learned from the benchmarking required to make the Doom project happen.
It's got MCP support, Perfetto, Speedscope, Treemap, duplicate package detection, and more.
It's got MCP support, Perfetto, Speedscope, Treemap, duplicate package detection, and more.
December 11, 2025 at 5:04 AM
TypeScript excitement 😉
The infamous Dimitri is cooking up a slick type analysis tool called TypeSlayer 🔥
"If you have a large enough project, there are performance problems where you can shave 100 seconds off CI by making a 5 line change. The problem is knowing out where to make that change."
The infamous Dimitri is cooking up a slick type analysis tool called TypeSlayer 🔥
"If you have a large enough project, there are performance problems where you can shave 100 seconds off CI by making a 5 line change. The problem is knowing out where to make that change."
Reposted by Daniel Rosenwasser
now in early-access/alpha/beta/gamma/whatever-you-wanna-call-it.
here's a walkthrough: youtu.be/IP6EZXzXBzY
here's a walkthrough: youtu.be/IP6EZXzXBzY
TypeSlayer - a TypeScript types performance tool
YouTube video by Michigan TypeScript
youtu.be
December 11, 2025 at 3:44 AM
now in early-access/alpha/beta/gamma/whatever-you-wanna-call-it.
here's a walkthrough: youtu.be/IP6EZXzXBzY
here's a walkthrough: youtu.be/IP6EZXzXBzY
Reposted by Daniel Rosenwasser
⚔️introducing TypeSlayer⚔️ A #typescript type performance benchmarking and analysis tool. A summation of everything learned from the benchmarking required to make the Doom project happen.
It's got MCP support, Perfetto, Speedscope, Treemap, duplicate package detection, and more.
It's got MCP support, Perfetto, Speedscope, Treemap, duplicate package detection, and more.
December 11, 2025 at 3:44 AM
⚔️introducing TypeSlayer⚔️ A #typescript type performance benchmarking and analysis tool. A summation of everything learned from the benchmarking required to make the Doom project happen.
It's got MCP support, Perfetto, Speedscope, Treemap, duplicate package detection, and more.
It's got MCP support, Perfetto, Speedscope, Treemap, duplicate package detection, and more.
Reposted by Daniel Rosenwasser
It’s amazing how quickly the Go version of TypeScript was created. The key “trick” of the TS team was to port, not to rewrite: 2ality.com/2025/03/type...
December 2, 2025 at 11:53 PM
It’s amazing how quickly the Go version of TypeScript was created. The key “trick” of the TS team was to port, not to rewrite: 2ality.com/2025/03/type...
Reposted by Daniel Rosenwasser
It’s good! My main task right now at Vanta (when not wrangling organizational growth stuff) is migrating all of our packages to it, even the ones doing crazy shenanigans that tsgo catches and tsc incorrectly let pass. (There are only a handful in our millions of lines of code.)
I repeat: it’s good!
I repeat: it’s good!
I'm sure many of you have already been trying out the native preview, but if you haven't, now is the best time to start!
We've got some updates on TypeScript 7! The new native port
- can type-check any project
- supports --build and --incremental
- has rich editor features implemented
- is still 10x faster
and is ready for you to try today!
devblogs.microsoft.com/typescript/p...
- can type-check any project
- supports --build and --incremental
- has rich editor features implemented
- is still 10x faster
and is ready for you to try today!
devblogs.microsoft.com/typescript/p...
December 2, 2025 at 7:57 PM
It’s good! My main task right now at Vanta (when not wrangling organizational growth stuff) is migrating all of our packages to it, even the ones doing crazy shenanigans that tsgo catches and tsc incorrectly let pass. (There are only a handful in our millions of lines of code.)
I repeat: it’s good!
I repeat: it’s good!
Reposted by Daniel Rosenwasser
TypeScript excitement 😉
News on the Go-based TS 7.0 🎉
🔷 Checker is very compatible with TS 5.9
🔷 Language Server maturity leapt forward
🔷 JS downlevel is limited: ES2021 now, ES2015 in future
🔷 JS checking gets stricter
🔷 No API access yet
News on the Go-based TS 7.0 🎉
🔷 Checker is very compatible with TS 5.9
🔷 Language Server maturity leapt forward
🔷 JS downlevel is limited: ES2021 now, ES2015 in future
🔷 JS checking gets stricter
🔷 No API access yet
We've got some updates on TypeScript 7! The new native port
- can type-check any project
- supports --build and --incremental
- has rich editor features implemented
- is still 10x faster
and is ready for you to try today!
devblogs.microsoft.com/typescript/p...
- can type-check any project
- supports --build and --incremental
- has rich editor features implemented
- is still 10x faster
and is ready for you to try today!
devblogs.microsoft.com/typescript/p...
Progress on TypeScript 7 - December 2025 - TypeScript
Earlier this year, the TypeScript team announced that we’ve been porting the compiler and language service to native code to take advantage of better raw performance, memory usage, and parallelism. Th...
devblogs.microsoft.com
December 2, 2025 at 6:02 PM
TypeScript excitement 😉
News on the Go-based TS 7.0 🎉
🔷 Checker is very compatible with TS 5.9
🔷 Language Server maturity leapt forward
🔷 JS downlevel is limited: ES2021 now, ES2015 in future
🔷 JS checking gets stricter
🔷 No API access yet
News on the Go-based TS 7.0 🎉
🔷 Checker is very compatible with TS 5.9
🔷 Language Server maturity leapt forward
🔷 JS downlevel is limited: ES2021 now, ES2015 in future
🔷 JS checking gets stricter
🔷 No API access yet
Reposted by Daniel Rosenwasser
I'm sure many of you have already been trying out the native preview, but if you haven't, now is the best time to start!
We've got some updates on TypeScript 7! The new native port
- can type-check any project
- supports --build and --incremental
- has rich editor features implemented
- is still 10x faster
and is ready for you to try today!
devblogs.microsoft.com/typescript/p...
- can type-check any project
- supports --build and --incremental
- has rich editor features implemented
- is still 10x faster
and is ready for you to try today!
devblogs.microsoft.com/typescript/p...
Progress on TypeScript 7 - December 2025 - TypeScript
Earlier this year, the TypeScript team announced that we’ve been porting the compiler and language service to native code to take advantage of better raw performance, memory usage, and parallelism. Th...
devblogs.microsoft.com
December 2, 2025 at 5:58 PM
I'm sure many of you have already been trying out the native preview, but if you haven't, now is the best time to start!
Reposted by Daniel Rosenwasser
A status update on the TypeScript rewrite
TL;DR - if you haven't tried it already, you should!
TL;DR - if you haven't tried it already, you should!
Progress on TypeScript 7 - December 2025 - TypeScript
Earlier this year, the TypeScript team announced that we’ve been porting the compiler and language service to native code to take advantage of better raw performance, memory usage, and parallelism. Th...
devblogs.microsoft.com
December 2, 2025 at 5:37 PM
A status update on the TypeScript rewrite
TL;DR - if you haven't tried it already, you should!
TL;DR - if you haven't tried it already, you should!
Reposted by Daniel Rosenwasser
We've got some updates on TypeScript 7! The new native port
- can type-check any project
- supports --build and --incremental
- has rich editor features implemented
- is still 10x faster
and is ready for you to try today!
devblogs.microsoft.com/typescript/p...
- can type-check any project
- supports --build and --incremental
- has rich editor features implemented
- is still 10x faster
and is ready for you to try today!
devblogs.microsoft.com/typescript/p...
Progress on TypeScript 7 - December 2025 - TypeScript
Earlier this year, the TypeScript team announced that we’ve been porting the compiler and language service to native code to take advantage of better raw performance, memory usage, and parallelism. Th...
devblogs.microsoft.com
December 2, 2025 at 5:48 PM
We've got some updates on TypeScript 7! The new native port
- can type-check any project
- supports --build and --incremental
- has rich editor features implemented
- is still 10x faster
and is ready for you to try today!
devblogs.microsoft.com/typescript/p...
- can type-check any project
- supports --build and --incremental
- has rich editor features implemented
- is still 10x faster
and is ready for you to try today!
devblogs.microsoft.com/typescript/p...
Reposted by Daniel Rosenwasser
who are all you people
November 24, 2025 at 4:22 AM
who are all you people
Reposted by Daniel Rosenwasser
FWIW we rolled out opt-in usage of the @typescriptlang.org native preview for in-editor workflows a few weeks ago at Vanta and the response has been extremely and overwhelmingly positive, the gaps in LSP support notwithstanding. I’m working on our blockers to just using it for all type checking.
We're hoping for TypeScript 6.0 early 2026 (think February or earlier) and 7.0 shortly after.
We're looking for people to use the native previews of 7.0 for feedback ASAP though. We feel the language service is pretty solid these days!
We're looking for people to use the native previews of 7.0 for feedback ASAP though. We feel the language service is pretty solid these days!
November 19, 2025 at 9:19 PM
FWIW we rolled out opt-in usage of the @typescriptlang.org native preview for in-editor workflows a few weeks ago at Vanta and the response has been extremely and overwhelmingly positive, the gaps in LSP support notwithstanding. I’m working on our blockers to just using it for all type checking.
Reposted by Daniel Rosenwasser
My #BazelCon 2025 talk about how Canva used isolatedDeclarations to greatly improve typecheck performance
youtu.be/26CoMExb6FE
youtu.be/26CoMExb6FE
Improving Bazel TypeScript Type-Checks With IsolatedDeclarations - Brad Zacher, Canva
YouTube video by BazelCon
youtu.be
November 14, 2025 at 8:48 PM
My #BazelCon 2025 talk about how Canva used isolatedDeclarations to greatly improve typecheck performance
youtu.be/26CoMExb6FE
youtu.be/26CoMExb6FE
Reposted by Daniel Rosenwasser
Today on the pod, Daniel Rosenwasser & Jake Bailey reveal what's coming in TypeScript 6 & 7! Learn about ES2024 defaults, the new Go compiler, and smarter DOM typings.
share.transistor.fm/s/ad05eae6
#typescript
share.transistor.fm/s/ad05eae6
#typescript
What's Coming in TypeScript 6/7 | Daniel Rosenwasser | Jake Bailey | Ep 43B | TypeScript.fm - The Friendly Show for TypeScript Developers | Episode 43
Daniel Rosenwasser and Jake Bailey join the two fools to talk about what's coming soon in TypeScript 6 and 7. What changes should developers expect? What might the new compiler API look like? How is the...
share.transistor.fm
November 13, 2025 at 3:49 PM
Today on the pod, Daniel Rosenwasser & Jake Bailey reveal what's coming in TypeScript 6 & 7! Learn about ES2024 defaults, the new Go compiler, and smarter DOM typings.
share.transistor.fm/s/ad05eae6
#typescript
share.transistor.fm/s/ad05eae6
#typescript
Reposted by Daniel Rosenwasser
Node excitement 😉
Congrats to @marcoippolito.dev on making it official: type-stripping in Node 25 is now declared to be stable 🎉
You can run: node index.ts
The capabilities have not changed since Node 24. This is purely a maturity indicator.
Congrats to @marcoippolito.dev on making it official: type-stripping in Node 25 is now declared to be stable 🎉
You can run: node index.ts
The capabilities have not changed since Node 24. This is purely a maturity indicator.
Type stripping is now stable.
Enjoy 🌞
Enjoy 🌞
November 12, 2025 at 7:12 AM
Node excitement 😉
Congrats to @marcoippolito.dev on making it official: type-stripping in Node 25 is now declared to be stable 🎉
You can run: node index.ts
The capabilities have not changed since Node 24. This is purely a maturity indicator.
Congrats to @marcoippolito.dev on making it official: type-stripping in Node 25 is now declared to be stable 🎉
You can run: node index.ts
The capabilities have not changed since Node 24. This is purely a maturity indicator.
Reposted by Daniel Rosenwasser
Type stripping is now stable.
Enjoy 🌞
Enjoy 🌞
November 12, 2025 at 5:07 AM
Type stripping is now stable.
Enjoy 🌞
Enjoy 🌞
Reposted by Daniel Rosenwasser
I'm pleased that this year's GitHub survey acknowledges that untyped & typed JavaScript deserve to be counted as part of the same ecosystem.
🔶 New repos (last 12 months): JS 9.3M, Python 9.3M, TS 5.4M
🔶 Contributor delta (last 12 months): TS +1.1M, Python +0.9M, JS +0.4M
🔶 Contributor count chart
🔶 New repos (last 12 months): JS 9.3M, Python 9.3M, TS 5.4M
🔶 Contributor delta (last 12 months): TS +1.1M, Python +0.9M, JS +0.4M
🔶 Contributor count chart
October 29, 2025 at 10:40 AM
I'm pleased that this year's GitHub survey acknowledges that untyped & typed JavaScript deserve to be counted as part of the same ecosystem.
🔶 New repos (last 12 months): JS 9.3M, Python 9.3M, TS 5.4M
🔶 Contributor delta (last 12 months): TS +1.1M, Python +0.9M, JS +0.4M
🔶 Contributor count chart
🔶 New repos (last 12 months): JS 9.3M, Python 9.3M, TS 5.4M
🔶 Contributor delta (last 12 months): TS +1.1M, Python +0.9M, JS +0.4M
🔶 Contributor count chart
Reposted by Daniel Rosenwasser
Big news in this year's GitHub Octoverse report: TypeScript is now the most-used language on GitHub!
We are thrilled and grateful to see the TypeScript and JavaScript community continue to grow and thrive. 🚀
Read up more at github.blog/news-insight...
We are thrilled and grateful to see the TypeScript and JavaScript community continue to grow and thrive. 🚀
Read up more at github.blog/news-insight...
Octoverse: A new developer joins GitHub every second as AI leads TypeScript to #1
In this year’s Octoverse, we uncover how AI, agents, and typed languages are driving the biggest shifts in software development in more than a decade.
github.blog
October 28, 2025 at 6:47 PM
Big news in this year's GitHub Octoverse report: TypeScript is now the most-used language on GitHub!
We are thrilled and grateful to see the TypeScript and JavaScript community continue to grow and thrive. 🚀
Read up more at github.blog/news-insight...
We are thrilled and grateful to see the TypeScript and JavaScript community continue to grow and thrive. 🚀
Read up more at github.blog/news-insight...
We are still looking for feedback on tsgo, but it is worth calling out we expect some type-checking changes that you may need to adapt to.
The native previews are easy to grab from npm, and are published nightly to try out!
www.npmjs.com/package/@typ...
The native previews are easy to grab from npm, and are published nightly to try out!
www.npmjs.com/package/@typ...
October 24, 2025 at 12:22 AM
We are still looking for feedback on tsgo, but it is worth calling out we expect some type-checking changes that you may need to adapt to.
The native previews are easy to grab from npm, and are published nightly to try out!
www.npmjs.com/package/@typ...
The native previews are easy to grab from npm, and are published nightly to try out!
www.npmjs.com/package/@typ...
Reposted by Daniel Rosenwasser
ECMAScript excitement 😉
@jason-williams.co.uk from TechAtBloomberg announces the release of Boa's Rust-based implementation of TC39 Stage 3 Temporal 🎉
Chrome estimates this will ship in Chromium 143 🎉🎉
Temporal is the shiny replacement for the broken JS Date API ✨
@jason-williams.co.uk from TechAtBloomberg announces the release of Boa's Rust-based implementation of TC39 Stage 3 Temporal 🎉
Chrome estimates this will ship in Chromium 143 🎉🎉
Temporal is the shiny replacement for the broken JS Date API ✨
Temporal_rs has been released!!!
This is the first public release of Temporal_rs, a Rust implementation of the Temporal API powering Boa, Kiesel, V8 plus other engines.
This will be shipping in Chromium soon
More info in our blog post: boajs.dev/blog/2025/09...
This is the first public release of Temporal_rs, a Rust implementation of the Temporal API powering Boa, Kiesel, V8 plus other engines.
This will be shipping in Chromium soon
More info in our blog post: boajs.dev/blog/2025/09...
Temporal_rs is here! The datetime library powering Temporal in Boa, Kiesel, and V8 | Boa JS
clock banner
boajs.dev
September 24, 2025 at 3:40 PM
ECMAScript excitement 😉
@jason-williams.co.uk from TechAtBloomberg announces the release of Boa's Rust-based implementation of TC39 Stage 3 Temporal 🎉
Chrome estimates this will ship in Chromium 143 🎉🎉
Temporal is the shiny replacement for the broken JS Date API ✨
@jason-williams.co.uk from TechAtBloomberg announces the release of Boa's Rust-based implementation of TC39 Stage 3 Temporal 🎉
Chrome estimates this will ship in Chromium 143 🎉🎉
Temporal is the shiny replacement for the broken JS Date API ✨
Reposted by Daniel Rosenwasser
