Takeaways from React Native EU 2019
A couple of weeks ago, the team developing Dagens Nyheter’s apps attended React Native EU in beautiful Wroclaw, Poland 🇵🇱. The event was organized by Callstack and we saw speakers from Facebook and Microsoft among others. This post will cover what we were the most excited about.
Types, types, types
For ages we wrote our apps with JavaScript but recently we have, as many others in the React Native community, moved towards TypeScript. Radek Czemerys gave a great talk about his experience of types, and TypeScript in particular, and we totally agree with some of his key findings; that types are crucial for large React Native codebases. Our largest app, Dagens Nyheter, is now over three years old and even though we have had almost the same team members since the beginning, we still struggle reviewing old code. For example, when looking at an old component it is not always that easy to understand what properties it needs and what the component actually does. Now, when we use TypeScript in all new features and new apps, we find ourselves having a more pleasant experience developing them. It is safer and it also improves team and codebase scalability.
Alexey Kureev also explained how types (Flow or TypeScript) plays a part in React Native’s new infrastructure (that is yet to be released). He talked about CodeGen, the new generator that can utilize the type definitions to generate the C++ protocols and interfaces needed in Fabric/TurboModules and in the JSI.
All in all, we are happy that we have started with TypeScript and that the React Native community has chosen the same path.
Hermes
The talk we were most excited about was Tzvetan Mikow’s, from Facebook, talk about Hermes, the new JavaScript engine for Android optimized for React Native. Since we first heard rumors of it on the Interwebs we understood that it will be a game changer. Luckily we were able to give it a go a couple of days before the conference and our minds were blown. Our apps became noticeably faster even on low end devices. So obviously we wanted to hear how this engine was engineered.
Tzetan explained that without Hermes, the bundled JavaScript code needs to be transformed into bytecode at runtime on the user’s device to be able to get executed. In this case, the translated bytecode is not optimized because the resources are limited on the user’s device and the translation needs to be fast due to the user do not want to wait. These factors obviously impact benchmarking values such as “Time to Interaction” (TTI). Hermes solves this by translating the JavaScript into bytecode in buildtime, such a “ahead-of-time compiler” can optimize the bytecode way more since it runs on the build computer that has more resources and more time. The benchmarking results can be seen in the picture above, for example TTI was decreased by a whopping 2.29 seconds, or over 50%! Well done Tzvetan and everybody else on the Hermes team!
Future of React Native
We believe that it’s safe to say that the future of React Native is awesome! Emily Janzer’s, from Facebook, talk “The New React Native” showed how Facebook is heavily invested in it and we look forward to the coming releases! Things as Hermes in React Native 0.60 and Fast Refresh in React Native 0.61 also shows that React Native is moving in a healthy direction.
During the conference we also learned that Microsoft is heavily invested in React Native. Micah Lewis and E.J. Layne from Microsoft and Catalin Miron from Skype talked in their respective talks how they use React Native in other platforms than the usual iOS and Android. Micah and E.J. showed us how they use React Native in Microsoft Office (!). That Microsoft and other large companies use React Native in this extension also shows that the future of React Native looks great.
Thank you!
We are happy that we attended React Native EU and thank you to Callstack for organizing and to Wroclaw for having us. Hopefully we will meet again next year!
