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Toward Hermes being the Default

· 12 min read
Xuan Huang
Xuan Huang
Software Engineer at Meta

Since we announced Hermes in 2019, it has been increasingly gaining adoption in the community. The team at Expo, who maintain a popular meta-framework for React Native apps, recently announced experimental support for Hermes after being one of the most requested features of Expo. The team at Realm, a popular mobile database, also recently shipped its alpha support for Hermes. In this post, we want to highlight some of the most exciting progress we've made over the past two years to push Hermes towards being the best JavaScript engine for React Native. Looking forward, we are confident that with these improvements and more to come, we can make Hermes the default JavaScript engine for React Native across all platforms.

Preparing Your App for iOS 15 and Android 12

· 3 min read
Samuel Susla
Samuel Susla
Software Engineer at Meta

Hello everyone!

With new mobile OS versions releasing late this year, we recommend preparing your React Native apps beforehand to avoid regressions when the releases become generally available.

React Native Is Hiring Managers, To Expand Beyond Mobile

· 2 min read
Eli White
Eli White
Software Engineer at Meta

We recently shared React Native’s Many Platform Vision for how expanding React to other platforms improves the framework for everyone else. We’ve been making significant progress on this vision over the last couple years by partnering with Microsoft on React Native for Windows and macOS, and Oculus on React Native in VR.

As part of our plans beginning earlier this year, we are growing our focus on these platforms and growing our teams to help us achieve our vision. In order to support our new teammates, and many more to come, we are hiring two Engineering Managers: one to help support React Native for Desktop, and one to support React Native for VR.

React Native's Many Platform Vision

· 8 min read
Christine Abernathy
Christine Abernathy
Developer Advocate at Meta
Eli White
Eli White
Software Engineer at Meta
Luna Wei
Luna Wei
Software Engineer at Meta
Timothy Yung
Timothy Yung
Software Engineer at Meta

React Native has been very successful at raising the bar for mobile development, both at Facebook and elsewhere in the industry. As we interact with computers in new ways and as new devices are invented, we want React Native to be there for everyone. Although React Native was originally created to build mobile apps, we believe that focusing on many platforms and building to each platform’s strengths and constraints has a symbiotic effect. We have seen huge benefits when we extended this technology to desktop and virtual reality, and we're excited to share what this means for the future of React Native.

React Native in H2 2021

· 6 min read
Luna Wei
Luna Wei
Software Engineer at Meta

Over the past year so much has changed in our world, React Native being no exception. We've welcomed new members to our team (whom we are excited to eventually meet in person!), our projects have matured and new opportunities have arisen. We're excited to share all this with you in this post and others to come!

At Facebook, our team works in half-year cycles. Each half we review our strategy, set plans, and share them internally. Today, we want to share our H2 plans with you, our community.

H2 2021 is an exciting half for React Native. Our areas of focus include nurturing the community, beginning to roll out the new architecture to open source, and pushing the technology forward.

Announcing React Native 0.65

· 3 min read
Luna Wei
Luna Wei
Software Engineer at Meta

Today we’re releasing React Native version 0.65 with a new version of Hermes, improvements to accessibility, package upgrades, and more.

What's new in Hermes 0.8?

Hermes, Facebook’s open source JavaScript VM optimized for React Native, has been upgraded to version 0.8.1. Some of the stand-out features in this release are:

You can find the full Hermes changelog here.

Follow steps here to opt-in your app to Hermes if you haven’t already to leverage these new features and gains!

Accessibility Fixes and Additions

Last year Facebook took the GAAD pledge to improve accessibility within React Native. 0.65 shares the results of this pledge and other accessibility wins! Some notable changes include:

  • Allow specification of high contrast light and dark values for iOS. See documentation for more details.
  • Added getRecommendedTimeoutMillis API on Android. This exposes a user’s preferred default timeout value as set in Android’s accessibility options and is for users who may need extra time to review or reach controls, etc.
  • General fixes to ensure TalkBack/VoiceOver properly announce UI states such as disabled and unselected on components.

You can follow along or contribute to our outstanding accessibility issues here!

Notable Dependency Version Updates and Gotchas

  • react-native-codegen version 0.0.7 is now needed as a devDependency in the package.json.
  • JCenter has been sunsetted and read-only now. We have removed JCenter as a maven repository and updated dependencies to use MavenCentral and Jitpack.
  • Upgraded OkHttp from v3 to v4.9.1. See Upgrading to OkHttp 4 for more details on changes.
  • Upgraded to Flipper 0.93 to support Xcode 12.5. See Flipper changelog here.
  • Android Gradle Plugin 7 support
  • Apple Silicon requires a linker workaround. See @mikehardy’s note about this.

Thank You!

This release includes over 1100 commits from 61 contributors. Thank you to everyone who has contributed and supported this release! You can find the full changelog here.

The GAAD Pledge - One Year Later

· 4 min read
Alexandra Marlette
Alexandra Marlette
GAAD Pledge Open Source Accessibility Community Manager for React Native

It has been one year since Facebook took the GAAD Pledge to make React Native accessible and the project has exceeded our expectations. We are excited to announce that this project will continue throughout 2021 and want to update everyone on our progress so far. Following a thorough analysis of the accessibility gaps in React Native last year, work began on filling these gaps.

We started with 90 outstanding gap analysis issues and from March 2021, when the project launched on GitHub, until now:

  • 11 issues have been closed by the community.

  • 19 issues were evaluated and closed by the React Native team.

  • 9 pull requests were merged.

  • 1 pull request was merged into the React Native docs.

We want to recognize and thank the React Native community for the significant progress towards a more accessible React Native over the past year. Every contributor's effort has counted in making progress on improving React Native Accessibility.

The GAAD Pledge - March Accessibility Issues Update

· 3 min read
Alexandra Marlette
Alexandra Marlette
GAAD Pledge Open Source Accessibility Community Manager for React Native

It has been four weeks since we reached out to the GitHub community with a thoroughly reviewed gap analysis and list of issues to improve React Native's accessibility. With the help of the React Native community, we are already making great progress on improving accessibility. Community members have been helping contributors, reviewing tests, and bringing attention to prior accessibility issues. Since March 8th the community has closed six issues with four pull requests and seven other pull requests are in the pipeline for review.

While this work continues, the React Native and Accessibility teams at Facebook are evaluating accessibility bugs and issues that were submitted prior to this initiative, to determine if they are already covered by our current gap analysis or if there are additional issues that need to be brought into the project. One new issue has already been discovered and moved into the project, four others directly mapped to existing issues and two others are expected to be closed by addressing existing issues that address the root cause of their issue.

Thank you to all the community members who have participated. You are truly moving the needle in making React Native more accessible for everyone!

Announcing React Native 0.64 with Hermes on iOS

· 4 min read
Mike Grabowski
Mike Grabowski
CTO and Co-Founder at Callstack

Today we’re releasing React Native 0.64 that ships with support for Hermes on iOS.

Hermes opt-in on iOS

Hermes is an open source JavaScript engine optimized for running React Native. It improves 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).

With this release, we are happy to announce that you can now use Hermes to build on iOS as well. To enable Hermes on iOS, set hermes_enabled to true in your Podfile and run pod install.

use_react_native!(
:path => config[:reactNativePath],
# to enable hermes on iOS, change `false` to `true` and then install pods
:hermes_enabled => true
)

Please keep in mind that Hermes support on iOS is still early stage. We are keeping it as an opt-in as we are running further benchmarking. We encourage you to try it on your own applications and let us know how it is working out for you!

Inline Requires enabled by default

Inline Requires is a Metro configuration option that improves startup time by delaying execution of JavaScript modules until they are used, instead of at startup.

This feature has existed and been recommended for a few years as an opt-in configuration option, listed in the Performance section of our documentation. We are now enabling this option by default for new applications to help people have fast React Native applications without extra configuration.

Inline Requires is a Babel transform that takes module imports and converts them to be inline. As an example, Inline Requires transforms this module import call from being at the top of the file to where it is used.

Before:

import {MyFunction} from 'my-module';

const MyComponent = props => {
const result = MyFunction();

return <Text>{result}</Text>;
};

After:

const MyComponent = props => {
const result = require('my-module').MyFunction();

return <Text>{result}</Text>;
};

More information about Inline Requires is available in the Performance documentation.

View Hermes traces with Chrome

Over the last year Facebook has sponsored the Major League Hacking fellowship, supporting contributions to React Native. Jessie Nguyen and Saphal Patro added the ability to use the Performance tab on Chrome DevTools to visualize the execution of your application when it is using Hermes.

For more information, check out the new documentation page.

Hermes with Proxy Support

We have added Proxy support to Hermes, enabling compatibility with popular community projects like react-native-firebase and mobx. If you have been using these packages you can now migrate to Hermes for your project.

We plan to make Hermes the default JavaScript engine for Android in a coming release so we are working to resolve the remaining issues people have when using Hermes. Please open an issue on the Hermes GitHub repo if there are remaining issues holding back your app from adopting Hermes.

React 17

React 17 does not include new developer-facing features or major breaking changes. For React Native applications, the main change is a new JSX transform enabling files to no longer need to import React to be able to use JSX.

More information about React 17 is available on the React blog.

Major Dependency Version Changes

  • Dropped Android API levels 16-20. The Facebook app consistently drops support for Android versions with sufficiently low usage. As the Facebook app no longer supports these versions and is React Native’s main testing surface, React Native is dropping support as well.
  • Xcode 12 and CocoaPods 1.10 are required
  • Minimum Node support bumped from 10 to Node 12
  • Flipper bumped to 0.75.1

Thanks

Thank you to the hundreds of contributors that helped make 0.64 possible! The 0.64 changelog includes all of the changes included in this release.