I'm a software and mobile developer (and of late I've been meddling with better U.I. (user interface)and U.X. (user experience) ) , I've personally found React Native to be an easier framework to developfor iphones and android smartphones, there are others like Xamerin (personal opinon, you'll spend more time trying to get things to work than your code),Kotlin, Ionic (which I'd love to hear about other developers experience with those two and how they compete in production and development).
Besides that, it's apart of the open-source side of Facebook development, as far as I know it follows React (also from facebook), thus far i haven't faced major problems in regards to it from development / production phase. It felt like quite an easy transition when I moved from a web-based project that I was working on back to mobile. However I do recommend learning about this thing called redux, which can serve as a form of state mangement and app data storage, allowing you to pull necessary data from it as you need it ( I'm still adjusting to it)...
But yeah overall, I think it will be one of the more dominating "frameworks" used for native development.
RE: Cross Platform Mobile application Development - React Native - Recommendation