The Jest integration I sneak-peeked earlier is also letting me roll out code coverage support. The coverage reporter is already in place. I just had to instrument the code and send the coverage data from the device back to the CLI. Surprisingly, it was really easy to implement!

Harness isn't a simple tool - it's a bunch of components working together to give the best DX for testing JS code with native modules. Maintaining all that as a solo dev isn't easy, so I tried offloading some work by using Jest's CLI to run Harness… and it worked!

We're hosting a livestream today, with a special focus on React Native Harness! Expect insider insights on how it all works and sneak peeks at what's coming next. 🗓️ Thu 16, 5 PM CEST See you there!

🎉 Introducing React Native Harness - a lightweight framework for testing native modules directly on device or emulator. Write tests in a Jest-like syntax, run them in a real React Native runtime, and verify native behavior without mocks.

Are you using the Performance API in React Native? If yes, I'm pretty sure you've wished a bunch of times that you could check out measures like you do in Chrome DevTools. What if I told you Rozenite is about to bring you that same vibe? Hot or not?

Yesterday, the community requested server-side event support for Rozenite's Network Activity. I said I'd look into it… but somehow ended up pushing a branch with the feature almost done. Whoops! 🙈

The Rozenite plugin family is growing, so I created a plugin directory! It includes both official plugins and community ones like rozenite-preview. Best part? You can add your own by opening a quick pull request on the Rozenite repo.

Just found out I'll be speaking at React Universe Conf! Rozenite's been out for a while, but in this talk, I'll dive deeper into how it works under the hood - how I hooked into DevTools without forking anything, and how you can build your own plugins too. Hope to see you there!

New week, new feature! Struggling to understand what's going on in your WebSocket connection? Fear not! Thanks to Rozenite, you'll soon be able to inspect WebSocket traffic and review each message one by one - whether it's text, binary, or JSON. Coming soon 🔥

Bronze trophy unlocked: 100 stars collected! It's not platinum (yet), but every legend starts somewhere 😉

Rozenite's Network Activity plugin got a major overhaul yesterday! The new UI and improved functionality make it much more convenient to use. You can now inspect request bodies and responses with an interactive JSON viewer 🚀

Rozenite is gaining traction - we've just crossed 50 stars on GitHub, and the number is steadily rising! It was included in the latest edition of the This Week in React newsletter, so if you slept through the release, it's high time you gave it a try and left a star while you're at it 🌟

Redux DevTools plugin for Rozenite is nearly complete. It offers basic debugging functionality, though without time travel or action dispatch capabilities. There's an upstream issue with the package that needs to be addressed first. github.com/callstackinc...

Rozenite - a plugin framework for React Native DevTools - is now live in alpha! 🎉 What started as a hacky PoC is now something you can use in real projects. Still lots to come: better network monitor, Redux DevTools, Re.Pack support & more 💪

Big news: the React Native DevTools framework is dropping by the end of this month 🔥 The name? It's locked in and I'm so excited about it. It kicks off a whole family of tools designed to push React Native even further… but I'm not allowed to say anything else at this point 🙊

Just found out I'll be speaking at React Advanced! I'll be sharing my journey hacking on React Native Devtools + building a plugin framework from scratch. If you're curious how it all came together, tune in! The live stream is free - just register here: gitnation.com/badges/react...

Built a file-based router for React Native - just for fun. It kinda works 😅 Learned a lot about Metro internals and found some cool low-level APIs along the way. Gave a talk about it! Check it out 👇 www.youtube.com/watch?v=oQjF...

Short RSC update: ✅ 'use client' and 'use server' now become proxies. ✅ Server rendering is... holding together with duct tape. Now to bundle client components and pray React Native accepts them 🙃

The sun’s out, the birds are singing... and I’m buried in last-minute tweaks to the playground app for today’s JavaScript Performance webinar 😅 Still time to grab a spot if you missed the announcement! 👇 streamyard.com/watch/pnM9CY...

Missing memoization where it matters most? Let’s fix that. Join us for Part 2 of our React Native JavaScript perfomance deep dive - debounce, selectors, state shape & more. 📅 Apr 29 • 6PM CET 🎙️ @grabbou.com + me 🎟️ streamyard.com/watch/pnM9CY...

Your React Native application slowed down? We are here to help you! Join our walkthrough of Callstack's 2025 Optimization Guide (Part 1). You will have the opportunity to ask questions and have them answered for free, without any hidden catches. streamyard.com/watch/VW8Ufy...

I'm gathering examples of situations where developers might choose popular tools or patterns without fully considering if they fit the project's needs. For instance, using SSR for dynamic dashboards where it's not really necessary. Got any ideas for similar examples? 🧐

Another hype cycle is starting. People are asking if they should learn Lynx, as it's being called a "React Native killer." It’s probably too early to say, but some influencers are already fueling the buzz for views and likes.

Lynx: a hit or a miss? Let's find out together. This is going to be fun 🔥

Been exploring visual regression testing tools for React Native lately and it feels like the space is underdeveloped. 🤔 What features would your dream visual regression tool have to make you want to use it?

Anyone know how to capture and stream an iOS simulator’s screen? It used to be possible with simctl a few years ago. I tried idb, but the stream is full of artifacts 🤔

We are going live in a few minutes! Join us to learn more about the state of React! www.youtube.com/watch?v=bIa8... @lukasz.app @psyche.social

We’re breaking down the "State of React 2024"! Hooks still cool, or did we go too far? Is React still king? 🤔 Join me, @psyche.social, and @chmal.it for some real talk! 📅 Tomorrow at 18:00 (GMT+1), 12:00 EST, 9:00 PST 📺 Watch: 🔴 YouTube: bit.ly/React2024Survey 🔴 Twitch: twitch.tv/callstack_live

Introducing metro-minify-swc 🚀 It’s an experimental package that replaces Terser with SWC for blazing-fast code minification. Use with caution and share your feedback ⚡️ github.com/V3RON/metro-...

Just switched from Terser to SWC in Metro. Saw nearly a 30% improvement in build time and even a slight reduction in size. Worth it 🔥

Sunday coding vibes: Aurora can now peek into your bundle and spot duplicated dependencies. Pretty neat!

Meet Aurora - my personal sidekick for making the best of React Native projects 🌟

Why did no one mention Synology NASes are this loud? My router is near my bedroom, and so is the NAS. Some nights, it’s noisy enough to pull me out of sleep ☹️

I just signed up for three runs this year: a 5km, a 10km, and, wait for it, a half marathon. I’m almost certain I’ll be questioning all my life choices the moment the starting whistle blows, lol

Struggling to inspect your Metro bundle in a bare React Native project? 🤔 I created a simple library that lets you use Expo Atlas without the full Expo setup! github.com/V3RON/expo-a... If it helps, consider leaving a star! 🌟

Did you know? Shared Workers let multiple tabs of the same website share a single Web Worker. Perfect for WebSocket apps - one connection, no matter how many tabs are open. Read more here: javascript.plainenglish.io/sharing-webs...

Need to adjust state based on props? Skip useEffect - call state setters directly during render. React will re-render immediately, boosting performance and avoiding stale state with new props. react.dev/learn/you-mi... See it in action here: j5kccn.csb.app

January’s barely started, but I think I’ve found my hack of the year! How to keep a Google Cast session alive when an iOS device locks? Normally, iOS kills network activity after about a minute. The solution? Loop a silent MP3 while the video plays. It sounds ridiculous, but hey - it works! 🚀

Ever had React DevTools freeze after starting a second profiling session? Good news: that bug is fixed! 🎉 Turns out, it was caused by two components fighting over a state variable, creating a re-render loop. The fix? One line of code 🙈 github.com/facebook/rea...

The team leader isn’t just there to assign tasks and demand results - they’re there to empower the team and make sure everyone has what they need to work well. A good team leader is like an older brother or sister, guiding and supporting the team. It's a pity not everyone understands that.

Me and the boys on our way to spread performance on underperforming tech projects 🚀

To improve performance, gather metrics, analyze, and act carefully. Avoid hasty decisions that waste time and resources. Start small, test thoroughly, and scale confidently. Opt for isolated changes over major refactors, which are more cost-effective and often sufficiently impactful.

modern web is so unoptimized. "old" reddit runs incredibly well on my computer, new reddit makes firefox scream and put up a message about how its causing slowdown

“What can I say that hasn’t been said already?” 🤔 Here’s the secret: A lot! Your “common knowledge” could be a game-changer for others. Submit that talk - it might kick off an incredible adventure. 🎤

Stuck on a train in the middle of nowhere with no electricity. Kraków doesn’t want to let me go that easily. 😩

Did you know packages can run lifecycle scripts, like postinstall, to do things like compile native code after installation? Sounds harmless, right? Think again! These scripts can hide malicious actions, even sneaking malware into other libraries. The good news? There’s a solution 🧵

I've been thinking about getting AWS certified for a while now. I’ve worked with several services like ECS, SNS, SQS, and S3, but still far from an expert. Time to change that! Just found out there's a 50% discount if I take the exam this year. Is it doable in a month if I really focus? 🤔

I’m honored to be named a Microsoft MVP! Huge thanks to @marcinmilewicz.bsky.social for inviting me to this program. This recognition inspires me to keep sharing knowledge and growing the developer community in Toruń, Poland, and beyond. Now, it’s time to roll up my sleeves and prove I’m worth it!

New features coming to React Render Measurement Tool! 🚀 You can now identify which components caused renders and even make assertions based on that info. Coming soon: custom matchers to make assertions super clean and readable.

It’s crazy how much I enjoy tech meetups. There’s just something about connecting with people who share the same passions, learning something new - even if I might never use it. It’s so energizing. But lately, I can’t help but notice how things are changing. Fewer meetups, fewer people showing up.