Easy interview questions in React Native, page 2
The JS thread and why it bottlenecks performance
A single thread runs your JS, React reconciliation, and event handling; blocking it delays updates and gestures, and it is separate from the UI thread.
FlatList and list virtualization
Use FlatList (or SectionList) which virtualizes, rendering only items near the viewport and recycling as you scroll, unlike ScrollView which mounts everything.
Cost of console.log and production-safe debugging
Each console.log serializes data and, when devtools are attached, crosses the bridge synchronously, blocking the JS thread; strip logs in release and use Flipper, dev tools, or remote crash and analytics tools.
How do you send a one-off event from native to JS?
Emit an event from native using an event emitter and subscribe in JS with NativeEventEmitter, or resolve a promise/callback for a single result.
What are the three pillars of the New Architecture?
JSI for direct JS-native calls, Fabric as the new renderer, and TurboModules for lazy native modules, all unified by CodeGen for type-safe bindings.
Unit testing vs component testing in React Native
Unit tests verify isolated functions/logic with Jest; component tests render components and assert behavior with React Native Testing Library.
iOS Provisioning Profiles and Signing Certificates
The certificate proves developer identity, the App ID names the app, the profile binds certificate, App ID, and devices.
Managing Per-Environment Configuration in React Native
Use per-environment env files plus build flavors or schemes, inject at build time, keep secrets off the device.
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