I've ran through most of the intro doc, but I'm still not sure if Exponent supports invoking platform/system APIs? E.g. if I want to access clipboard contents, or wifi network configuration, etc, how can it be done with Exponent? With React Native, I can write corresponding functionalities using Java or Swift/ObjC, and then integrate it with the RN main app, but how can this be done with Exponent?
For now, Exponent just lets you write things that only use JS, and we make that easy and reliable and straightforward. We actually think this is the best way to write most apps that can be built this way since the code is easier to maintain and works cross platform, and you can do things like instant updates much more reliably when all your code is JS.
We're looking at a way you can write Java/Swift/Obj-C extensions for Exponent, but that will take us some time.
With Exponent you write just JavaScript. In addition to most of the APIs that come with React Native, Exponent provides several APIs (https://docs.getexponent.com/versions/latest/sdk/index.html) and we're steadily adding more. If there's a native API we don't have yet that developers need, they tell us about it and we add it to our roadmap.
Exponent is open-source, too, so if you needed to you could fork it and write your own native code or make a raw React Native app. We recommend writing pure JS apps if you can, though. At Exponent we write native code so other people don't have to.