Does React Native compile JavaScript into Java for Android?

Basically, Javascript communicates with native components (Java on Android, Objective C on iOS, C# on Windows).

The communication occurs through the so-called “bridge“. If at any time you feel that this communication slows things down too much, you can choose to implement the Javascript functionality in Java, Objective C or C# respectively in order to run purely native. In this case, you are writing directly in native code, so there’s no Javascript to native compilation.