How React Native works
A React Native app has two parts. The logic and screen definitions are written in JavaScript or TypeScript — just like in React web projects. The buttons, lists, input fields, and screen transitions, however, are real native iOS and Android components that the framework creates based on your code.
Recent versions of React Native significantly reworked how the JavaScript layer talks to the operating system, making it faster and more predictable. For most business apps, users can't tell the difference from fully native performance.
React Native is often paired with Expo — a toolkit that handles builds, code signing, and access to the camera, notifications, files, and other device features. It makes getting started and shipping updates noticeably easier.
Benefits of React Native
- Familiar technologies. JavaScript and TypeScript are among the most widely used programming languages, so it's easier to find developers or hand the project off to another team.
- Code shared with the web. Data types, API calls, form validation rules, copy, and translations can be used in both the website and the app.
- Native UI components. Input fields, scrolling, and toggles behave the way users of each platform expect.
- Fast fixes. Changes to the JavaScript layer can be delivered to users without a new App Store or Google Play release — within the limits of Apple's and Google's policies.
- Large community. Ready-made libraries exist for most common needs — payments, maps, analytics, social login.
Drawbacks and risks
- Reliance on third-party libraries. Many features come from community libraries. If a maintainer stops supporting one, replacing it becomes your problem.
- Tricky upgrades. Moving a long-neglected project to a new React Native version can take real effort: dependencies and build settings change along with the framework.
- Complex graphics and animation. Games, photo or video editors, and animation-heavy interfaces are better built natively or with other tools.
- Native expertise is still required. Custom features need developers who know Swift and Kotlin; otherwise, the project hits the limits of off-the-shelf libraries.
React Native vs. Flutter
Both frameworks let you build a high-quality app from a single codebase. The choice usually comes down not to technical details but to your business context:
- if you have a React web product and a team developing it, React Native delivers more value through shared code and know-how;
- if the app has a complex custom design that must be pixel-identical on every device, Flutter is often the better fit;
- if neither applies, we compare the available libraries for your features and the experience of the team that will maintain the product.
For more on when a single codebase for two platforms makes sense at all, see our page on cross-platform apps.
Expo or bare React Native
For most new projects, we recommend Expo: less manual iOS and Android configuration, simpler builds, and faster updates. Expo now supports custom native modules too, so the old "you can't do anything custom with Expo" limitation no longer applies.
We work without Expo when a project has long existed that way, when full control over the native layer is needed, or when the app is embedded in an existing native project.
App performance
Complaints about "slow React Native" usually have less to do with the framework than with how the code is written. Typical causes: long lists that render every item at once, unnecessary screen re-renders, heavy uncached images, and animations running in JavaScript instead of at the native level.
We measure exactly what's slowing things down on real budget smartphones, not just on developers' high-end phones. After fixes, we compare the results against the baseline so the improvement is measurable, not just claimed.
New project or upgrading an existing one
For a new app, we set up TypeScript, well-planned navigation, and only actively maintained libraries from day one. If there's a React web version, we agree on which parts of the code will be shared and how to keep them in sync.
Existing apps often come to us with an outdated framework version, unmaintained libraries, and a build that barely works. First, we restore a stable build, then upgrade React Native step by step so the app can still be released between stages.
Publishing and life after launch
A React Native app goes through the same App Store and Google Play review as a native one. We prepare the builds, store listings, and data collection disclosures for both platforms.
After launch, it's important to keep the framework and libraries up to date: the longer you wait, the more expensive the upgrade. We can take this on as part of app support.
What affects the cost
- Code shared with the web: whether there's anything to reuse and how ready it is for reuse.
- Number and complexity of screens: standard forms and lists or custom animations.
- Native modules: how many features aren't covered by existing libraries.
- Backend: whether the same API as the website is enough or new endpoints are needed.
- State of an existing project: React Native version, number of outdated dependencies, test coverage.
We provide an estimate after reviewing the features and, for existing apps, a technical audit.
Frequently asked questions
Can we reuse code from our React website? Logic, data types, and API code — yes. UI components will need to be rebuilt, because the app uses native components instead of HTML.
Can we update the app without store review? Small changes to the JavaScript layer — yes, as long as they don't change the app's core purpose. New native features are still published the usual way.
Our app is on an old React Native version. Does it need a rewrite? Usually not. Upgrading step by step is typically cheaper and safer than rewriting from scratch.
Is React Native suitable for a large product? Yes, many large apps run on it. What matters is a well-thought-out code structure and careful library selection.
Why Promodex
Promodex has delivered 750+ projects since 2015; our mobile work includes Idram, as well as Fuelio and Omio, which we contributed to. Our in-house team includes designers and mobile and web developers, so your mobile app and React website can evolve in sync. We don't outsource work, and we continue supporting the app after launch.
