React Native

A performance problem that only shows up for five percent of users on specific device models never surfaces in local profiling, yet it measurably costs App Store ratings and retention. Firebase Performance Monitoring and New Relic Mobile close that gap by continuously collecting performance data from the real production fleet. This article covers which metrics both tools capture automatically, how to set up custom traces for critical user flows like checkout or login, and what sensible alerting thresholds look like for a production app.

The App Store review guidelines are not a form you check off once, they are a living rulebook Apple reapplies at every submission. React Native apps tend to stumble over the same handful of rejection reasons: incomplete builds, missing privacy declarations, and the suspicion of being nothing more than a web wrapper. This guide walks through the most relevant guidelines in detail and shows how to avoid typical rejections from the very start.

A Jest test run happens on Node.js and cannot execute Swift or Kotlin code, yet a lot of React Native logic depends directly on native modules: camera, location, biometrics, push notifications. Anyone who does not cleanly mock these dependencies ends up either with unsolvable test failures or with tests that silently verify nothing at all. This article covers concrete mock strategies for native modules in Jest, a running example with a camera module, and where the line between a meaningful unit test and a necessary end-to-end test actually sits.

Reanimated Layout Animations automatically compute smooth transitions the moment a component's size, position, or visibility changes, without developers manually orchestrating start and end values through useState or useEffect. This article covers entering, exiting, and layout transitions using a list with add and remove animations as an example, plus the performance limits for very complex lists.

Dark mode is no longer a nice-to-have, it's a user expectation. Hardcoding colors directly into StyleSheet.create in React Native builds up technical debt the moment dark mode or a second color scheme is required. Design tokens, a central ThemeProvider, and systematic theming solve this problem once, cleanly.

Apollo Client connects GraphQL and React Native through a normalizing cache, typed hooks, and a persistence layer that keeps data available across app restarts. Configuring ApolloClient, InMemoryCache, and the Apollo hooks correctly means fewer network roundtrips, instant UI feedback through optimistic updates, and an app that stays usable even on flaky mobile connections.

The New Architecture replaces the old asynchronous bridge and its JSON serialization with JSI, a direct C++ interface between JavaScript and native code. Fabric takes over as the new renderer for synchronous layout, TurboModules load native modules lazily instead of eagerly at app startup, and Codegen generates type-safe interfaces for both platforms from a single TypeScript spec file.

Functional tests verify that a component does the right thing, but say nothing about whether it looks right. A shifted button, an incorrectly scaled icon, or a contrast bug introduced during a refactor slip past Jest assertions unnoticed. Visual regression testing closes that gap by comparing screenshots against a maintained baseline and surfacing every pixel-level deviation. This article walks through the practical toolchain around Detox, how to manage baseline images, and how to systematically avoid false positives caused by animations and timestamps.

The Expo Modules API replaces hand-written React Native bridging with a declarative Swift and Kotlin DSL for building custom native modules without manual bridging boilerplate. This article covers the architecture, a full hands-on example, and the limits of testing inside Expo Go.

An app on a television has no concept of touch, no swipe gesture and no tap, only a remote control with directional buttons and a select button that moves a visible focus ring from one element to the next. Anyone porting an existing React Native app unchanged to Android TV or tvOS quickly runs into buttons that cannot be selected and lists that lose focus while scrolling. This article covers how focus management works as the central concept, how existing touch components get adapted for it, and where Android TV and tvOS genuinely differ as target platforms.