After over 20 pull requests from 6 contributors in the React Native Community, we're excited to launch react-native doctor, a new command to help you out with getting started, troubleshooting and automatically fixing errors with your development environment. The doctor command is heavily inspired by Expo and Homebrew's own doctor command with a pinch of UI inspired by Jest.
We’re excited to announce React Native 0.61, which includes a new reloading experience we’re calling Fast Refresh.
When we asked the React Native community about common pain points, one of the top answers was that the “hot reloading” feature was broken. It didn’t work reliably for function components, often failed to update the screen, and wasn’t resilient to typos and mistakes. We heard that most people turned it off because it was too unreliable.
In React Native 0.61, we’re unifying the existing “live reloading” (reload on save) and “hot reloading” features into a single new feature called “Fast Refresh”. Fast Refresh was implemented from scratch with the following principles:
To see Fast Refresh in action, check out this video:
Give it a try, and let us know what you think! If you prefer, you can turn it off in the Dev Menu (Cmd+D on iOS, Cmd+M or Ctrl+M on Android). Turning it on and off is instant so you can do it any time.
Here are a few Fast Refresh tips:
// @refresh reset comment to the file with that component.console.log or a debugger statement during edits is a neat debugging technique.Please report any issues with Fast Refresh on GitHub, and we’ll look into them.
act, and more. See the React 16.9 blog post for an automated migration script and more information.Thanks to all of the contributors that helped make 0.61 possible!
To see all the updates, take a look at the 0.61 changelog.
Last week at Chain React we announced Hermes, an open source JavaScript engine we’ve been working on at Facebook. It’s a small and lightweight JavaScript engine optimized for running React Native on Android. Check it out!
Hermes improves React Native performance by decreasing memory utilization, reducing download size, and decreasing the time it takes for the app to become usable or “time to interactive” (TTI).
“As we analyzed performance data, we noticed that the JavaScript engine itself was a significant factor in startup performance and download size. With this data in hand, we knew we had to optimize JavaScript performance in the more constrained environments of a mobile phone compared with a desktop or laptop. After exploring other options, we built a new JavaScript engine we call Hermes. It is designed to improve app performance, focusing on our React Native apps, even on mass-market devices with limited memory, slow storage, and reduced computing power.” —Hermes: An open source JavaScript engine optimized for mobile apps, starting with React Native
Want to get started right away? Be sure to check out our new guide to enabling Hermes in your existing React Native app in the docs!
Illustration by Rachel Nabors
After months of hard work from hundreds of contributors, the React Native Core team is proud to announce the release of version 0.60. This release handles significant migrations for both Android and iOS platforms, and many issues are resolved too. This blog post covers the highlights of the release. As always though, refer to the changelog for more detailed information. Finally, thank you contributors for helping us to make this milestone!
There have been many improvements to the accessibility APIs, like announceForAccessibility, plus improvements to roles, action support, flags, and more. Accessibility is a complex science, but we hope these improvements make it a bit easier to be an A11Y. Be sure to check React Native Open Source Update June 2019 for more details of these changes.
React Native's start screen has been updated! Thank you to the many contributors who helped create the new UI. This new "Hello World" will welcome users to the ecosystem in a more friendly, engaging way.
AndroidX is a major step forward in the Android ecosystem, and the old support library artifacts are being deprecated. For 0.60, React Native has been migrated over to AndroidX. This is a breaking change, and your native code and dependencies will need to be migrated as well.
With this change, React Native apps will need to begin using AndroidX themselves. They cannot be used side-by-side in one app, so all of the app code and dependency code needs to be using one or the other.
While your own native code will need to be migrated by you, @mikehardy, @cawfree, and @m4tt72 built a clever tool named "jetifier" to patch your node_modules. Library maintainers will need to upgrade, but this tool provide you with a temporary solution while giving them time to release an AndroidX version. So if you find errors related to AndroidX migration, give this a shot.
CocoaPods are now part of React Native's iOS project. If you weren't already, be sure to open iOS platform code using the xcworkspace file from now on (protip: try xed ios from the root project directory). Also, the podspecs for the internal packages have changed to make them compatible with the Xcode projects, which will help with troubleshooting and debugging. Expect to make some straightforward changes to your Podfile as part of the upgrade to 0.60 to bring this exciting support. Note that we are aware of a compatibility issue with use_frameworks!, and we're tracking an issue with workarounds and a future patch.
WebView and NetInfo were previously extracted into separate repositories, and in 0.60 we’ve finished migrating them out of the React Native repository. Additionally, in response to community feedback about new App Store policy, Geolocation has been extracted. If you haven’t already, complete your migration by adding dependencies to react-native-webview, @react-native-community/netinfo, and @react-native-community/geolocation. If you'd like an automated solution, consider using rn-upgrade-deprecated-modules. Maintainers have made more than 100 commits to these repositories since extraction and we’re excited to see the community’s support!
The team working on the React Native CLI has introduced major improvements to native module linking called autolinking! Most scenarios will not require the use of react-native link anymore. At the same time, the team overhauled the linking process in general. Be sure to react-native unlink any preexisting dependencies as mentioned in the docs above.
@lucasbento, @pvinis, @kelset, and @watadarkstar have built a great tool called Upgrade Helper to make the upgrade process simpler. It helps React Native users with brownfield apps or complex customizations to see what's changed between versions. Take a look at the updated upgrading docs and try it out today for your upgrade path!
Changes for AndroidX will almost certainly require updates to your library, so be sure to include support soon. If you're not able to upgrade yet, consider checking your library against the jetifier to confirm that users are able to patch your library at build time.
Review the autolinking docs to update your configs and readme. Depending on how your library was previously integrated, you may also need to make some additional changes. Check the dependencies guide from the CLI for information on how to define your dependency interface.
While these are the highlights that we noted, there are many others to be excited about. To see all the updates, take a look at the changelog. As always, stay tuned for more news. Enjoy 0.60 in the meantime!
In the past six months, a total of 2800 commits were made to React Native by more than 550 contributors. 400 contributors from the community created more than 1,150 Pull Requests, of which 820 Pull Requests were merged.
The average number of Pull Requests per day throughout the past six months has increased from three to about six, even though we split the website, CLI and many modules out of React Native via the Lean Core effort. The average amount of open pull requests is now below 25 and we usually reply with suggestions and reviews within hours or days.
We’d like to highlight a number of recent contributions which we thought were awesome:
clickable prop and an onClick callback for invoking actions via keyboard navigation (note: this will soon be renamed to focusable).The primary motivation of Lean Core has been to split modules out of React Native into separate repositories so they can receive better maintenance. In just a six months repositories like WebView, NetInfo, AsyncStorage, the website and the CLI received more than 800 Pull Requests combined. Besides better maintenance, these projects can also be independently released more often than React Native itself.
We have also taken the opportunity to remove obsolete polyfills and legacy components from React Native itself. Polyfills were necessary in the past to support language features like Map and Set in older versions of JavaScriptCore (JSC). Now that React Native ships with a new version, these polyfills were removed.
This work is still in progress and many more things still need to be split out or removed both on the native and JavaScript side but there are early signs that we managed to reverse the trend of increasing the surface area and app size: When looking at the JavaScript bundle for example, about a year ago in version 0.54 the React Native JavaScript bundle size was 530kb and grew to 607kb (+77kb) by version 0.57 in just 6 months. Now we are seeing a bundle size reduction of 28kb down to 579kb on master, a delta of more than 100kb!
As we conclude the first iteration of the Lean Core effort, we will make an effort to be more intentional about new APIs added to React Native and we will continuously evaluate ways to make React Native smaller and faster, as well as finding ways to empower the community to take ownership of various components.
Six months ago we asked the community “What do you dislike about React Native?” which gave a good overview of problems people are facing. We replied to the post a few months ago and it's time to summarize the progress that was made on top issues:
Unfortunately we weren’t able to improve everything just yet:
Given the large amount of changes in the past six months, we'd like to ask you the same question again. If you are using the latest version of React Native and you have things you'd like to give feedback on, please comment on our new edition of “What do you dislike about React Native?”
Facebook merges all Pull Requests and internal changes directly into Facebook’s repository first and then syncs all commits back to GitHub. Facebook’s infrastructure is different from common continuous integration services and not all open source tests were run inside of Facebook. This means that commits that sync out to GitHub frequently break tests in open source which take a lot of time to fix.
Héctor Ramos from the React Native team spent the past two months improving React Native's continuous integration systems both at Facebook and on GitHub. Most of the open source tests are now run before changes are committed to React Native at Facebook which will keep CI stable on GitHub when commits are being synchronized.
Make sure to check out our talks about the future of React Native! In the next couple of months, members of the React Native team at Facebook will speak at Chain React and at React Native EU. Also, watch out for our next release, 0.60, which is right around the corner. It's going to be exciting ✨
This week, Eli White gave a talk at F8 2019 about React Native in Facebook's Android and iOS applications. We are excited to share what we've been up to for the past two years and what we're doing next.
Check out the video on Facebook's developer website:
Eli's talk concludes by talking about our recent open source work. We gave an update on our progress in March and recently Nader Dabit and Gant Laborde invited Christoph for a chat on their podcast, React Native Radio, to chat about React Native in open source.
You'll find the episode in your favorite podcasting app soon or you can listen to the recording right here:
Welcome to the 0.59 release of React Native! This is another big release with 644 commits by 88 contributors. Contributions also come in other forms, so thank you for maintaining issues, fostering communities, and teaching people about React Native. This month brings a number of highly anticipated changes, and we hope you enjoy them.
React Hooks are part of this release, which let you reuse stateful logic across components. There is a lot of buzz about hooks, but if you haven't heard, take a look at some of the wonderful resources below:
- Introducing Hooks explains why we’re adding Hooks to React.
- Hooks at a Glance is a fast-paced overview of the built-in Hooks.
- Building Your Own Hooks demonstrates code reuse with custom Hooks.
- Making Sense of React Hooks explores the new possibilities unlocked by Hooks.
- useHooks.com showcases community-maintained Hooks recipes and demos.
Be sure to give this a try in your apps. We hope that you find the reuse as exciting as we do.
React Native uses JSC (JavaScriptCore) to power your application. JSC on Android was a few years old, which meant that a lot of modern JavaScript features weren't supported. Even worse, it performed poorly compared iOS's modern JSC. With this release, that all changes.
Thanks to some awesome work by @DanielZlotin, @dulmandakh, @gengjiawen, @kmagiera, and @kudo JSC has caught up with the past few years. This brings with it 64-bit support, modern JavaScript support, and big performance improvements. Kudos for also making this a maintainable process now so that we can take advantage of future WebKit improvements without so much legwork, and thank you Software Mansion and Expo for making this work possible.
We want to help people have performant React Native apps by default and are working to bring Facebook's optimizations to the community. Applications load resources as needed rather than slowing down launch. This feature is called "inline requires", as it lets Metro identify components to be lazy loaded. Apps with a deep and varied component architecture will see the most improvement.
We need the community to let us know how it works before we turn it on by default. When you upgrade to 0.59, there will be a new metro.config.js file; flip the options to true and give us your feedback! Read more about inline requires in the performance docs to benchmark your app.
React Native is a large and complex project with a complicated repository. This makes the codebase less approachable to contributors, difficult to test, and bloated as a dev dependency. Lean Core is our effort to address these issues by migrating code to separate libraries for better management. The past few releases have seen the first steps of this, but let's get serious.
You may notice that additional components are now officially deprecated. This is great news, as there are now owners for these features actively maintaining them. Heed the warning messages and migrate to the new libraries for these features, because they will be removed in a future release. Below is a table indicating the component, its status, and where you may migrate your use to.
| Component | Deprecated? | New home |
|---|---|---|
| AsyncStorage | 0.59 | @react-native-community/react-native-async-storage |
| ImageStore | 0.59 | expo-file-system or react-native-fs |
| MaskedViewIOS | 0.59 | @react-native-community/react-native-masked-view |
| NetInfo | 0.59 | @react-native-community/react-native-netinfo |
| Slider | 0.59 | @react-native-community/react-native-slider |
| ViewPagerAndroid | 0.59 | @react-native-community/react-native-viewpager |
Over the coming months, there will be many more components following this path to a leaner core. We're looking for help with this — head over to the lean core umbrella to pitch in.
React Native's command line tools are developer's entry point to the ecosystem, but they had long-standing issues and lacked official support. The CLI tools have been moved to a new repository, and a dedicated group of maintainers have already made some exciting improvements.
Logs are formatted much better now. Commands now run nearly instantly — you'll immediately notice a difference:
We heard your feedback regarding the React Native upgrade process and we are taking steps to improve the experience in future releases. To upgrade to 0.59, we recommend using rn-diff-purge to determine what has changed between your current React Native version and 0.59, then applying those changes manually. Once you've upgraded your project to 0.59, you will be able to use the newly improved react-native upgrade command (based on rn-diff-purge!) to upgrade to 0.60 and beyond as newer releases become available.
Android support in 0.59 has been cleaned up following Google's latest recommendations, which may result in potential breakage of existing apps. This issue might present as a runtime crash and a message, "You need to use a Theme.AppCompat theme (or descendant) with this activity". We recommend updating your project's AndroidManifest.xml file, making sure that the android:theme value is an AppCompat theme (such as @style/Theme.AppCompat.Light.NoActionBar).
The react-native-git-upgrade command has been removed in 0.59, in favor of the newly improved react-native upgrade command.
Lots of new contributors helped with enabling generation of native code from flow types and resolving Xcode warnings - these are a great way to learn how React Native works and contributing to the greater good. Thank you! Look out for similar issues in the future.
While these are the highlights that we noted, there are many others to be excited about. To see all of the updates, take a look at the changelog. 0.59 is a huge release – we can't wait for you to try it out.
We have even more improvements coming throughout the rest of the year. Stay tuned!
Ryan and the whole React Native core team
We announced our React Native Open Source roadmap in Q4 2018 after deciding to invest more in the React Native open source community.
For our first milestone, we focused on identifying and improving the most visible aspects of our community. Our goals were to reduce outstanding pull requests, reduce the project's surface area, identify leading user problems, and establish guidelines for community management.
In the past two months, we made more progress than we expected. Read on for more details:
In order to build a healthy community, we must respond quickly to code contributions. In past years, we de-prioritized reviewing community contributions and accumulated 280 pull requests (December 2018). In the first milestone, we reduced the number of open pull requests to ~65. Simultaneously, the average number of pull requests opened per day increased from 3.5 to 7 which means we have handled about 600 pull requests in the last three months.
We merged almost two-thirds and closed one-third of the pull requests. They were closed without being merged if they are obsolete or low quality, or if they unnecessarily increase the project's surface area. Most of the merged pull requests fixed bugs, improved cross-platform parity, or introduced new features. Notable contributions include improving type safety and the ongoing work to support AndroidX.
At Facebook, we run React Native from master, so we test all changes first before they make it into a React Native Release. Out of all the merged pull requests, only six caused issues: four only affected internal development and two were caught in the release candidate state.
One of the more visible community contributions was the updated “RedBox” screen. It's a good example of how the community is making the developer experience friendlier.
React Native currently has a very wide surface area with many unmaintained abstractions that we do not use a lot at Facebook. We are working on reducing the surface area in order to make React Native smaller and allow the community to take better care of abstractions that are mostly unused at Facebook.
In the first milestone, we asked the community for help on the Lean Core project. The response was overwhelming and we could barely keep up with all the progress. Check out all the work completed in less than a month!
What we are most excited about is that maintainers have jumped in fixing long standing issues, adding tests, and supporting long requested features. These modules are getting more support than they ever did within React Native, showing that this is a great step for the community. Examples of such projects are WebView that has received many pull requests since their extraction and the CLI that is now maintained by members of the community and received much needed improvements and fixes.
In December, we asked the community what they disliked about React Native. We aggregated the responses and replied to each and every problem. Fortunately, many of the issues that our community faces are also problems at Facebook. In our next milestone, we plan to address some of the main problems.
One of the highest voted problems was the developer experience of upgrading to newer versions of React Native. Unfortunately, this is not something that we experience ourselves because we run React Native from master. Thankfully, members from the community already stepped up to address this problem:
Without the help of the React Native community, especially Mike Grabowski and Lorenzo Sciandra, we would not be able to ship releases. We want to improve the release management process and plan to be more involved from now on:
Many of these plans will be incorporated in the upcoming React Native 0.59 release. 0.59 will ship with React Hooks, a new 64-bit version of JavaScriptCore for Android, and many performance and functionality improvements. It is currently published as a release candidate and is expected to be stable within the next two weeks.
For the next two months, we will continue managing pull requests to stay on track while also starting to reduce the number of outstanding GitHub issues. We will continue reducing the surface area of React Native through the Lean Core project. We plan to address 5 of the top community problems. As we finalize the community guidelines, we will turn attention to our website and documentation.
We are very excited to host over ten contributors from our community at Facebook London in March to help drive several of these efforts. We are glad that you are using React Native and hope that you'll see and feel the improvements we are working on in 2019. We'll be back with another update in a few months and will be merging your pull requests in the meantime! ⚛️✌️
In 2018 the React Native Community made a number of changes to the way we develop and communicate about React Native. We believe that a few years from now we will look back and see that this shift was a turning point for React Native.
A lot of people are excited about the rewrite of React Native's architecture, widely known as Fabric. Among other things, this will fix fundamental limitations in React Native's architecture and will set up React Native for success in the future together with JSI and TurboModules.
The biggest shift in 2018 was to empower the React Native Community. From the beginning, Facebook encouraged developers from all around the world to participate in React Native's open source project. Since then, a number of core contributors emerged to handle, among other things, the release process.
These members took a few substantial steps towards making the whole community more empowered to shape the future of this project with the following resources:
react-native-releases 📬This repository, created in January, serves the dual purpose of allowing everyone to keep up the new releases in a more collaborative manner and opened the conversation of what would be part of a certain release to whomever wanted to suggest a cherry-pick (like for 0.57.8 and all its previous versions).
This has been the driving force behind moving away from a monthly release cycle, and the "long term support" approach currently used for version 0.57.x.
Half of the credit for reaching these decisions goes to the other repository created this year:
discussions-and-proposals 🗣This repository, created in July, expanded on the idea of a more open environment for conversations on React Native. Previously, this need was handled by issues labelled For Discussion in the main repository, but we wanted to expand this strategy to an RFC approach that other libraries have (e.g. React).
This experiment immediately found its role in the React Native lifecycle. The Facebook team is now using the community RFC process to discuss what could be improved in React Native, and coordinate the efforts around the Lean Core project - among other interesting discussions.
We are aware that our approach to communicate these efforts has not been as effective as we would have liked, and in an attempt to give you all an easier time keeping up with everything going on in the React Native Community (from releases to active discussions) we created a new twitter account that you can rely on @ReactNativeComm.
If you are not on that social network, remember that you can always watch repositories via GitHub; this feature improved these past few months with the possibility of being notified only for releases, so you should consider using it anyway.
Over the past 7-8 months, core contributors enhanced the React Native Community GitHub organization to take more ownership over the development of React Native, and enhance collaboration with Facebook. But this always lacked the formal structure that similar projects may have in place.
This organization can set the example for everyone in the larger developer community by enforcing a set of standards for all the packages/repos hosted in it, providing a single place for maintainers to help each other and contribute quality code that conforms to community-agreed standards.
In early 2019, we will have this new set of guidelines in place. Let us know what you think in the dedicated discussion.
We are confident that with these changes, the community will become more collaborative so that when we reach 1.0, we will all continue to write (even more) awesome apps by leveraging this joint effort 🤗
I hope you are as excited as we are about the future of this community. We're excited to see all of you involved either in the conversations happening in the repositories listed above or via the awesome code you’ll produce.
Happy coding!
This year, the React Native team has focused on a large scale re-architecture of React Native. As Sophie mentioned in her State of React Native post, we've sketched out a plan to better support the thriving population of React Native users and collaborators outside of Facebook. It's now time to share more details about what we've been working on. Before I do so, I'd like to lay out our long-term vision for React Native in open source.
Our vision for React Native is...
We have identified the following focus areas to help us achieve this vision.
Our goal is to reduce the surface area of React Native by removing non-core and unused components. We'll transfer non-core components to the community to allow it to move faster. The reduced surface area will make it easier to manage contributions to React Native.
WebView is an example of a component that we transferred to the community. We are working on a workflow that will allow internal teams to continue using these components after we remove them from the repository. We have identified dozens more components that we'll give ownership of to the community.
The React Native development experience for product teams at Facebook can be quite different from open source. Tools that may be popular in the open source community are not used at Facebook. There may be an internal tool that achieves the same purpose. In some cases, Facebook teams have become used to tools that do not exist outside of Facebook. These disparities can pose challenges when we open source our upcoming architecture work.
We'll work on releasing some of these internal tools. We'll also improve support for tools popular with the open source community. Here's a non-exhaustive list of projects we'll tackle:
When Facebook engineers publish code, it's considered safe to land if it passes all tests. These tests identify whether a change might break one of our own React Native surfaces. Yet, there are differences in how Facebook uses React Native. This has allowed us to unknowingly break React Native in open source.
We'll shore up our internal tests to ensure they run in an environment that is as close as possible to open source. This will help prevent code that breaks these tests from making it to open source. We will also work on infrastructure to enable better testing of the core repo on GitHub, enabling future pull requests to easily include tests.
Combined with the reduced surface area, this will allow contributors to merge pull requests quicker, with confidence.
Facebook will consume React Native via the public API, the same way open source does, to reduce unintentional breaking changes. We have started converting internal call sites to address this. Our goal is to converge on a stable, public API, leading to the adoption of semantic versioning in version 1.0.
React Native is one of the top open source projects on GitHub by contributor count. That makes us really happy, and we'd like to keep it going. We'll continue working on initiatives that lead to involved contributors, such as increased transparency and open discussion. The documentation is one of the first things someone new to React Native will encounter, yet it has not been a priority. We'd like to fix that, starting with bringing back auto-generated API reference docs, creating additional content focused on creating quality user experiences, and improving our release notes.
We're planning to land these projects throughout the next year or so. Some of these efforts are already ongoing, such as JSI which has already landed in open source. Others will take a bit longer to complete, such as reducing the surface area. We'll do our best to keep the community up to date with our progress. Please join us in the Discussions and Proposals repository, a initiative from the React Native community that has led to the creation of several of the initiatives discussed in this roadmap.