Tamagui basically solves the part of styling + rendering UI. It works on both web and native.
As for logic/data fetching...this has gotten far, far better in React over the past few years.
For data fetching, assuming you're using REST, @tanstack/react-query is incredible. It gives you a "hook" to wrap any async function, and returns loading states, errors, etc.
In the past, people used Redux, but it's out of fashion now. I prefer a library called zustand whenever I need non-data related global state management.
I would definitely disagree with "Redux is out of fashion". Redux is still by far the most widely used state management lib with React apps, by a very large margin - my estimates are that 35-40% of React apps use Redux, and no other state management lib appears to be over 10% [0].
We also get a lot of very positive feedback on our modern Redux Toolkit package, which we designed to simplify Redux usage [1], and it includes our "RTK Query" data fetching and caching API as well [2], which is similar to React Query in use case and API.
Mostly things that are very widely used in industry are indeed no longer “in fashion”. Instead they were in fashion and actually proved valuable enough to have staying power (as opposed to most fashionable things that are junk). Charitably, anyway — sometimes it seems you can’t tell why something is still widely used.
Probably the mentioned hooks-based approaches are indeed fashionable now. Remains to be seen whether they’ll stick around.
My team at work has completely rewritten from Redux with Redux Form to Tanstack query and React Hook Form over the past two years, and we don’t miss a single thing about Redux.
We make an app that contacts lots of microservices in sequence and combines the data in many ways. Having automatic refetching, caching and the like by default makes a world of difference.
I don't know if it's still the case but when I started my career (granted, some decades ago) using the new hotness X/Motif + C++, there were still more lines of COBOL around than anything else. (Hell, might not have been the case then, but that was the yarn.)
RTK Query is an excellent package! Coming from the React Query world, I inherited an RTK Query project and was initially disappointed, but have come to prefer it over (the also excellent) React Query.
Tamagui for "View" components and styling (+SSR on web)
+ React Query for data fetching, cache management, and neat hooks to use that data in apps. (+SSR on web
+ Zustand - "lite" state management on RN and React Web
+ Moti for X-Platform animations
+ Zeego for X-Platform menus
= Ridiculously high percentage of code re-use across web and react-native apps.
Those seem mostly non-reusable?