Facebook has released React Native 0.65. The framework for developing mobile applications offers new accessibility features such as a higher-contrast color mode for iOS. React Native also has the Hermes JavaScript engine version 0.8 in its luggage, and this in turn comes up with a brand new garbage collector.

New features for accessibility

By agreeing to the GAAD Pledge (Global Accessibility Awareness Day), Facebook promised last year to make React Native more accessible. The GAAD Pledge is a Project launched by the digital agency Diamond. By joining, companies and developers can make a promise that they attach a central role to accessibility in their open source projects.

The concrete effects in React Native 0.65 concern, among other things, a higher-contrast color display in iOS: For the DynamicColorIOS-Function can now not only be the mandatory colors light and dark but optionally also the corresponding, highly contrasting colors highContrastLight and highContrastDark. Which color can be seen in runtime then depends on the current system display and the accessibility settings.

DynamicColorIOS({
  light: color,
  dark: color,
  highContrastLight: color, // (optional) will fallback to "light" if not provided
  highContrastDark: color // (optional) will fallback to "dark" if not provided
});

The new API is now available to Android developers getRecommendedTimeoutMillis to disposal. It shows the default timeout value set in the Android input help by users who may have increased it, for example, if they need more time to reach a button.

The current processing status of these and other accessibility features in React Native can be checked with an overview on GitHub.

Hermes 0.8: Hades replaces GenGC

In addition to the accessibility innovations, React Native 0.65 also has Hermes version 0.8 on board. The open source JavaScript engine originates from Facebook’s development department as does React Native and is intended for use with the framework.

Hermes 0.8 uses a new Concurrent Garbage Collector by default, with the naming of which Facebook remains in the Greek world of legends: Hades should offer up to 30 times shorter break times on 64-bit devices. Most of the garbage collection uses a background thread that runs at the same time as the interpreter executing the JavaScript code. The previous garbage collector called GenGC, on the other hand, used a single thread shared with the interpreter.

The new version of Hermes on Android also contains the ECMAScript Internationalization API (ECMA-402 or Intl), which is enabled by default. The new API is intended to allow language-sensitive functions and is based on established internationalization APIs such as those of the Internationalization Components for Unicode (ICU) Library in .NET or the Java platform. There are also innovations for Hermes on iOS, which can now be used with the Mac Catalyst software and with Macs that are equipped with Apple’s in-house ARM processor M1 – which is already competing with Intel.

More information about React Native 0.65 can be found in a blog entry, all new features in Hermes 0.8 shows the changelog on GitHub.

(May)