Is there any documentation about JSI?

[samrith-s]

I am exploring moving to the new architecture at our company, and was wondering if we have any documentation about JSI and the React Native Core someplace.

We have developers who are comfortable with C++, Java/Kotlin, Objective-C/Swift and would love to move some of our stuff over to the new architecture but are finding it difficult to grasp as there is no documentation surrounding it.

[cipolleschi]

Hi @samrith-s, thanks for your question!

I am exploring moving to the new architecture at our company, and was wondering if we have any documentation about JSI and the React Native Core someplace.

What kind of documentation would you like to have? We were not planning to have it, given that it is some internal details and you users won't have to deal with JSI directly. But if you help us out, understanding which kind of information you would like to find there, we can think about writing it and plan some work accordingly.

In the mean time, the source code for JSI is open source, and can be explored here.

[cipolleschi]

Hi @samrith-s, out of curiosity, have you tried to develop a TurboModule using a pure C++ implementation? This allows you to:

• Use JSI without using it directly, as @sammy-SC was suggesting
• Share code between all the platforms you need

[teodorciuraru]

@cipolleschi I tried. Whatever method you create in C++, you must redefine it (marshal inside) inside the platforms—at least with the current create-react-native-library template, resulting in duplication. I switched to implementing native module + JSI which has C++ as the only source of truth, but I had to reverse engineer a lot of stuff because documentation was lacking.

[cipolleschi]

Have you had a look at the documentation on how to create a pure C++ turbomodule? Would this be a good solution for the problem?

[teodorciuraru]

@cipolleschi Yep. It looks more like how to add pure C++ TurboModule to an RN app, not how to create a Turbo Module library with only a C++ source of truth – that can be used inside other projects. I'm not sure if it's expected to create an RN library project only from that sample. I, myself, find it non-trivial to do. What I find missing is a create-react-native-library TurboModules with pure C++ (no platform marshaling).

[cortinico]

@teodorciuraru here a sample repository with a standalone C++ TurboModule that works with autolinking (at least on Android). Adding iOS support should be that hard https://github.com/cortinico/reproducer-cxx-tm-autolinking