Thread by @kzzzf

RN 0.59 has been released yesterday. One of the highlights is 64bit support and new JavaScriptCore provided via jsc-android-buildscripts project that my team @swmansion took a part in. I'd like to shed some light on how this change may impact you and your app.

thread 👇

Did you know that old JavaScript VM shipped with RN was from 2013? You could've used a much more up to date version since summer 2017 via github.com/react-native-c… project (and many people did) – in fact if your app is based on @expo you are already using new JSC.

If you are not already using new JSC, after 0.59 upgrade your Android RN app will likely perform better. You can also start relying on modern JS APIs like Proxies which weren’t supported in the 2013 JSC version and has been utilized by some popular JS libraries (e.g. mobx 5)

You app will get bigger – prepare for bigger APKs in particular. APK files typically include builds for all CPU architectures. Previously it was armv7 and x86 and now it will also contain arm64 and x86-64 binaries (on top of that 64bit binaries are bigger than 32bit counterparts)

Larger APK size may impact the installation speed. If you frequently reinstall app during development (instead of using JS reload or hot reload) you will likely experience that. Consider setting up "abi filters" for your debug builds or use "app bundle" (read on for details)

APK size increase is sth your users will experience too when installing an update (if you use "abi splitting" you are good to go). I recommend you check "android app bundle" format which allows google play to split your app per CPU arch automatically developer.android.com/studio/build/b…

With jsc-android-buildscript your JSC VM could have (almost) full i18n support (collation, localized date/currency formats etc) for a cost of some extra MBs of the app size. Check out our readme here for details github.com/react-native-c…