React Native Research & Evidence-Based Practice 2

Question 1

Which tool does the React Native team officially recommend for measuring JavaScript thread performance in production apps?

Accepted Answer

React Native Perf Monitor (in-app overlay)

Answer

The built-in in-app Performance Monitor (shake menu → Show Perf Monitor) is the officially recommended first-line tool for measuring JS and UI thread FPS in production-like conditions.

Question 2

Research consistently shows that unnecessary re-renders are a top cause of React Native jank. Which hook is the primary evidence-based solution for memoizing expensive child components?

Accepted Answer

React.memo

Answer

React.memo wraps a component and shallowly compares props, preventing re-renders when props have not changed, which is the standard evidence-based fix for unnecessary child re-renders.

Question 3

According to React Native documentation and community benchmarks, which bridge-related architecture improvement was introduced to eliminate serialization overhead?

Accepted Answer

JSI (JavaScript Interface)

Answer

JSI (JavaScript Interface) allows JavaScript to hold direct references to C++ host objects, eliminating the JSON serialization overhead of the old async bridge.

Question 4

A team wants evidence-based guidance on whether to use FlatList or ScrollView for a list of 500+ items. What does research on React Native memory usage recommend?

Accepted Answer

FlatList, because it virtualizes the list and only renders visible items

Answer

FlatList uses virtualization to keep only visible items in memory, which is the evidence-backed approach for long lists to prevent out-of-memory crashes.

Question 5

Studies on React Native app startup time show that switching to which JavaScript engine can reduce TTI (Time to Interactive) by up to 2× on Android?

Accepted Answer

Hermes

Answer

Hermes, Meta's purpose-built JS engine for React Native, pre-compiles JavaScript to bytecode at build time, dramatically reducing parse time and TTI on Android.

React Native Practice Test

React Native Practice Test

React Native Research & Evidence-Based Practice 2