React Native Component Lifecycle Deep Dive | Dataford Interview Questions

Context

You’re on a fintech mobile team shipping a React Native app with 5M+ monthly active users. A new “instant card controls” screen (freeze/unfreeze, spending limits) is causing intermittent bugs: duplicate network calls, stale UI after navigation, and occasional memory leaks from listeners.

These issues often come down to misunderstanding the lifecycle of a React Native component—especially how React schedules renders, when effects run, and how cleanup interacts with navigation and app backgrounding.

Core Question

Walk me through the lifecycle of a React Native component from creation to destruction, and tie it to real behaviors:

Mount phase: What happens from initial render through commit? When do useEffect and useLayoutEffect run? Where do subscriptions and initial fetches belong?
Update phase: What triggers a re-render (props/state/context)? How does React batch updates, and what does “render must be pure” mean? How do effects re-run and clean up on dependency changes?
Unmount phase: What runs during teardown? How do you prevent memory leaks (timers, event listeners, native subscriptions)?

Scope Guidance (what depth is expected)

Answer for both function components (hooks) and class components.
Include the distinction between render and commit phases.
Mention React Native-specific considerations (navigation focus, AppState, native event emitters) without going into platform APIs.
Call out common pitfalls (infinite loops, stale closures, double-invocation in Strict Mode, and cleanup mistakes).

Problem

Context

Core Question

Walk me through the lifecycle of a React Native component from creation to destruction, and tie it to real behaviors:

Mount phase: What happens from initial render through commit? When do useEffect and useLayoutEffect run? Where do subscriptions and initial fetches belong?
Update phase: What triggers a re-render (props/state/context)? How does React batch updates, and what does “render must be pure” mean? How do effects re-run and clean up on dependency changes?
Unmount phase: What runs during teardown? How do you prevent memory leaks (timers, event listeners, native subscriptions)?

Scope Guidance (what depth is expected)

Answer for both function components (hooks) and class components.
Include the distinction between render and commit phases.
Mention React Native-specific considerations (navigation focus, AppState, native event emitters) without going into platform APIs.
Call out common pitfalls (infinite loops, stale closures, double-invocation in Strict Mode, and cleanup mistakes).

Problem

Context

Core Question

Walk me through the lifecycle of a React Native component from creation to destruction, and tie it to real behaviors:

Mount phase: What happens from initial render through commit? When do useEffect and useLayoutEffect run? Where do subscriptions and initial fetches belong?
Update phase: What triggers a re-render (props/state/context)? How does React batch updates, and what does “render must be pure” mean? How do effects re-run and clean up on dependency changes?
Unmount phase: What runs during teardown? How do you prevent memory leaks (timers, event listeners, native subscriptions)?

Scope Guidance (what depth is expected)

Answer for both function components (hooks) and class components.
Include the distinction between render and commit phases.
Mention React Native-specific considerations (navigation focus, AppState, native event emitters) without going into platform APIs.
Call out common pitfalls (infinite loops, stale closures, double-invocation in Strict Mode, and cleanup mistakes).

Problem

Context

Core Question

Walk me through the lifecycle of a React Native component from creation to destruction, and tie it to real behaviors:

Mount phase: What happens from initial render through commit? When do useEffect and useLayoutEffect run? Where do subscriptions and initial fetches belong?
Update phase: What triggers a re-render (props/state/context)? How does React batch updates, and what does “render must be pure” mean? How do effects re-run and clean up on dependency changes?
Unmount phase: What runs during teardown? How do you prevent memory leaks (timers, event listeners, native subscriptions)?

Scope Guidance (what depth is expected)

Answer for both function components (hooks) and class components.
Include the distinction between render and commit phases.
Mention React Native-specific considerations (navigation focus, AppState, native event emitters) without going into platform APIs.
Call out common pitfalls (infinite loops, stale closures, double-invocation in Strict Mode, and cleanup mistakes).