{"checkpoints":{"s-rn-1":[{"q":"

A product manager asks whether Trailhead’s list will “feel native” or “feel like a website in an app”. What’s the accurate answer?

","options":[{"text":"It will feel like a website, because React Native renders HTML inside a WebView.","why":"There is no WebView or HTML involved. React Native renders platform views."},{"text":"It depends on whether you enable the New Architecture in app.json.","why":"The New Architecture is the only architecture in current React Native; there is nothing to enable, and it doesn’t decide whether views are native."},{"text":"It will use real platform views, so scrolling, text selection and inputs behave like other apps on the phone.","why":"Correct. Your components describe the UI; React Native creates and updates native views from that description."},{"text":"It will feel native on iOS and like a website on Android.","why":"Both platforms get native views. Android isn’t rendered differently."}],"answer":2},{"q":"

You install react-native-keyboard-controller in Trailhead, save, and the app crashes in Expo Go with a message that a native module can’t be found. What’s going on?

","options":[{"text":"The library needs Fast Refresh to be turned off.","why":"Fast Refresh only swaps JavaScript. The missing piece is native code."},{"text":"You need to run npx expo start --clear to rebuild the native code.","why":"Clearing the Metro cache resets JavaScript bundling; it never compiles native code."},{"text":"Expo Go only supports libraries written in TypeScript.","why":"Language isn’t the issue. Expo Go can only run native code that was compiled into Expo Go itself."},{"text":"The library contains native code that Expo Go doesn’t include, so you need a development build of your own app.","why":"Correct. A development build compiles the native modules your project uses, with the same dev tools as Expo Go."}],"answer":3},{"q":"

Which snippet renders a hike’s stats without crashing when hike.elevationM is 0?

","options":[{"text":"<View><Text>{hike.distanceKm} km</Text>{hike.elevationM > 0 && <Text>{hike.elevationM} m up</Text>}</View>","why":"Correct. Every string sits inside a Text, and the condition is a real boolean, so 0 renders nothing."},{"text":"<View><Text>{hike.distanceKm} km</Text>{hike.elevationM && <Text>{hike.elevationM} m up</Text>}</View>","why":"When elevation is 0, 0 && … evaluates to 0, which React Native tries to render as text directly inside the View."},{"text":"<View>{hike.distanceKm} km<Text>{hike.elevationM} m up</Text></View>","why":"The distance and “km” are raw text inside a View, which throws for every hike."}],"answer":0},{"q":"

A tester says the Save button on Trailhead’s quick-log form “sometimes doesn’t notice taps” while walking. The button is a 28-point-tall Pressable. What should you change first?

","options":[{"text":"Replace Pressable with the built-in Button component.","why":"Button can’t be styled to fit the design, and it doesn’t solve the size problem."},{"text":"Make the touch area at least 44 points tall, with padding or hitSlop, and give pressed feedback.","why":"Correct. Small targets are hard to hit on the move; a bigger area and instant feedback fix both halves of the complaint."},{"text":"Switch to onLongPress so accidental taps are ignored.","why":"That makes every save slower and doesn’t help users hit the target."}],"answer":1},{"q":"

Trailhead stores the distance input with const [km, setKm] = useState(0) and onChangeText={(t) => setKm(Number(t))}. Users can’t type “8.4”. Why?

","options":[{"text":"onChangeText doesn’t fire for decimal points.","why":"It fires for every change, including the dot."},{"text":"keyboardType must be set to number for decimals to work.","why":"That value doesn’t exist; the issue is the state, not the keyboard."},{"text":"Typing “8.” becomes Number("8."), which is 8, so the dot disappears from the controlled input before the user can add the 4.","why":"Correct. Keep the raw string in state and parse it when you need the number."},{"text":"TextInput values are limited to integers on Android.","why":"TextInput values are always strings, on both platforms."}],"answer":2}],"s-rn-2":[{"q":"

A teammate writes style={{ padding: '12px 16px', fontSize: '15px' }} on Trailhead’s card. What should the review comment say?

","options":[{"text":"Use rem units so text scales with accessibility settings.","why":"React Native has no rem units. Text already scales with the user’s font settings."},{"text":"Move these values into a CSS file imported at the top of the component.","why":"React Native doesn’t load CSS files; styles are JavaScript objects."},{"text":"It’s fine; React Native converts CSS strings automatically.","why":"It doesn’t. Multi-value strings and px units are either errors or ignored."},{"text":"Use unitless numbers and longhand keys: paddingVertical: 12, paddingHorizontal: 16, fontSize: 15.","why":"Correct. One unitless number per property, measured in points."}],"answer":3},{"q":"

A screen shows a ScrollView inside a View. The ScrollView’s content is cut off at the bottom and won’t scroll. The ScrollView has style={{ flex: 1 }}. What’s missing?

","options":[{"text":"overflow: 'scroll' on the ScrollView.","why":"ScrollView scrolls by itself; overflow styles don’t create scrolling."},{"text":"contentContainerStyle={{ flex: 1 }}","why":"That stretches the content to the viewport height, which often stops scrolling rather than fixing it."},{"text":"flex: 1 on the parent View, so the ScrollView inherits a bounded height to scroll within.","why":"Correct. Without a bounded parent, the ScrollView grows to its content and the screen cuts it off."},{"text":"horizontal={false}","why":"That is already the default."}],"answer":2},{"q":"

Trailhead’s settings screen has no header, and on a recent Android phone the title sits under the status bar clock. What’s the correct fix?

","options":[{"text":"Pad the content with useSafeAreaInsets().top from react-native-safe-area-context.","why":"Correct. Android draws apps edge to edge, so screens without a header must apply the top inset themselves."},{"text":"Use SafeAreaView from react-native.","why":"It’s deprecated and only ever applied padding on iOS."},{"text":"Add marginTop: 24, the height of the Android status bar.","why":"Status bar heights vary by device and setting; a hard-coded value is wrong on many phones."},{"text":"Hide the status bar on Android.","why":"Users lose the clock and battery level, and gesture areas at the bottom still overlap."}],"answer":0},{"q":"

Trailhead’s list rows each have an “expanded” toggle stored in useState inside the row. Which bug will users eventually report?

","options":[{"text":"Rows expand on iOS but not on Android.","why":"State works the same on both platforms; nothing here is platform-specific."},{"text":"Expanded rows collapse by themselves after scrolling far away and back.","why":"Correct. FlatList unmounts distant rows to save memory, and their local state is lost with them."},{"text":"The app crashes when two rows are expanded.","why":"Several rows can hold state at once without problems."}],"answer":1},{"q":"

Which change most improves a FlatList of 800 hikes where each row shows a 4000-pixel photo scaled down to a 56-point thumbnail?

","options":[{"text":"Increase windowSize to keep more rows mounted.","why":"More mounted rows means more full-size images in memory, which makes it worse."},{"text":"Wrap the FlatList in a ScrollView so it renders once.","why":"That disables virtualization and renders every row with its huge image."},{"text":"Replace FlatList with SectionList.","why":"SectionList is also a virtualized list; the images would cost the same."},{"text":"Load small thumbnail versions of the photos for the list, ideally with a caching image component like expo-image.","why":"Correct. Decoding huge images for tiny thumbnails wastes memory and time on every visible row."}],"answer":3}],"s-rn-3":[{"q":"

Trailhead needs a screen at /hikes/42/photos. Which file creates it?

","options":[{"text":"src/app/hikes/photos/[id].tsx","why":"That serves /hikes/photos/42, with the segments in the wrong order."},{"text":"src/app/(hikes)/[id]/photos.tsx","why":"A group in parentheses adds no URL segment, so this serves /42/photos."},{"text":"src/app/hikes/[id]/photos.tsx","why":"Correct. Each folder is a segment, and [id] captures the 42."},{"text":"src/components/HikePhotos.tsx","why":"Files outside src/app are never routes."}],"answer":2},{"q":"

In the detail screen, const { id } = useLocalSearchParams<{ id: string }>() and useHike(Number(id)) is called. A link arrives for /hikes/abc. What should the screen show?

","options":[{"text":"A red error screen, because Number(“abc”) throws.","why":"Number(“abc”) doesn’t throw; it returns NaN, and no hike matches."},{"text":"A friendly “hike not found” state, because the lookup returns nothing and the screen handles that case.","why":"Correct. Params are untrusted strings, so every screen with params needs a not-found state."},{"text":"The first hike in the list, as a fallback.","why":"Showing the wrong hike is worse than saying it doesn’t exist."},{"text":"Nothing; Expo Router refuses to match non-numeric ids.","why":"A dynamic segment matches any value; validation is your job."}],"answer":1},{"q":"

After a hike is deleted on its detail screen, the code calls router.push('/'). What problem does this create?

","options":[{"text":"A second copy of the log is pushed on top of the first, so the back gesture returns to the deleted hike’s screen.","why":"Correct. Use router.back() (or replace) so the deleted screen leaves the stack."},{"text":"The tab bar disappears permanently.","why":"Pushing a route doesn’t remove the tab layout."},{"text":"The hikes reducer runs twice.","why":"Navigation doesn’t dispatch actions; the duplication is in the stack, not the state."}],"answer":0},{"q":"

Which statement about Trailhead’s HikesProvider with separate state and dispatch contexts is true?

","options":[{"text":"Components that read hikes never re-render when hikes change.","why":"They do re-render; that’s how they show the new list."},{"text":"It makes the reducer run on a background thread.","why":"Reducers run on the JS thread like all React code."},{"text":"It removes the need to return new arrays from the reducer.","why":"Immutability is still required; React compares references."},{"text":"A delete button that only uses dispatch doesn’t re-render when the list changes, because the dispatch context never changes.","why":"Correct. dispatch is stable, so components that read only it skip list updates."}],"answer":3},{"q":"

On iOS, users of Trailhead’s add-hike form must tap Save twice whenever the keyboard is open. Which prop fixes it?

","options":[{"text":"autoFocus on the Save button.","why":"Buttons don’t take focus that way; the first tap is still swallowed."},{"text":"behavior="height" on the KeyboardAvoidingView.","why":"That changes how the layout avoids the keyboard, not how taps are handled."},{"text":"keyboardShouldPersistTaps="handled" on the ScrollView that contains the form.","why":"Correct. Taps on buttons then go through while the keyboard is open."},{"text":"submitBehavior="blurAndSubmit" on the last input.","why":"That affects the return key, not taps on the Save button."}],"answer":2}],"s-rn-4":[{"q":"

Trailhead’s explore screen shows “Could not load trails” even though the API responds. The server logs a 200. Debugging shows res.ok is true but the list is empty. Which state should the screen have shown?

","options":[{"text":"Error, because an empty response is a failure.","why":"The request succeeded; nothing failed."},{"text":"Loading, until at least one trail arrives.","why":"The request finished; staying in loading would spin forever."},{"text":"Error, with a Retry button, to try another server.","why":"Retrying a successful request returns the same empty list."},{"text":"Success with zero items, rendered as an empty state like “No trails within 50 km”.","why":"Correct. Empty is a successful result that deserves its own designed message."}],"answer":3},{"q":"

Where should Trailhead keep the user’s chosen units (km or mi)?

","options":[{"text":"expo-secure-store, because every setting is personal data.","why":"SecureStore is for secrets like tokens; a unit preference isn’t sensitive."},{"text":"AsyncStorage (or expo-sqlite/kv-store), as part of a small JSON preferences value.","why":"Correct. Small, non-secret preferences are what key-value storage is for."},{"text":"A new SQLite table with one row and one column.","why":"It works, but it’s heavier than needed for a single preference."},{"text":"An EXPO_PUBLIC_ environment variable.","why":"Those are fixed at build time for every user; they can’t store a user’s choice."}],"answer":1},{"q":"

A Trailhead user denied location permanently, later enabled it in Settings, and returned to the app. The tracking screen still says location is off. What’s the likely bug?

","options":[{"text":"The screen checked the permission only once when it mounted, instead of again when it regained focus.","why":"Correct. Re-check with getForegroundPermissionsAsync() in useFocusEffect or when the app returns to the foreground."},{"text":"iOS needs the app to be reinstalled before a permission change applies.","why":"Permission changes in Settings apply immediately to the installed app."},{"text":"canAskAgain must be reset to true in the app’s storage.","why":"The OS owns that value; your app only reads it."}],"answer":0},{"q":"

Trailhead v3 adds a difficulty column to the hikes table. A teammate edits the version 0 block of the migration to include the new column. What happens to existing users?

","options":[{"text":"They get the new column automatically on next launch.","why":"Their database is already past version 0, so that block never runs for them."},{"text":"Their hike log is deleted and recreated.","why":"Nothing deletes it; the edited block simply doesn’t run."},{"text":"Nothing changes for them, so queries that use difficulty fail with “no such column”.","why":"Correct. Add a new versioned step (ALTER TABLE … ADD COLUMN) instead of editing a shipped one."},{"text":"SQLite rejects the database file at startup.","why":"The file is valid; it just lacks the new column."}],"answer":2},{"q":"

A tracked hike shows 14 km for a walk the hiker knows was 9 km. The route has many sharp zigzags under forest cover. What’s the best fix?

","options":[{"text":"Switch to Accuracy.Lowest to save battery.","why":"Lower accuracy makes readings worse, not better."},{"text":"Round each coordinate to three decimal places.","why":"That snaps points to a coarse grid of roughly 100 m, which adds its own error."},{"text":"Ignore readings whose coords.accuracy exceeds a threshold before adding them to the route.","why":"Correct. Low-quality readings cause the zigzags; filtering them keeps the distance honest."},{"text":"Multiply the result by a correction factor of 0.65.","why":"A fixed factor is wrong for every other hike."}],"answer":2}],"s-rn-5":[{"q":"

Trailhead feels sluggish. The Performance Monitor (from the dev menu) shows the UI thread dropping frames while the JS thread is fine. Which cause fits?

","options":[{"text":"A component re-renders on every keystroke.","why":"Re-renders are JavaScript work; they would show as JS thread drops."},{"text":"Very large images decoded and drawn for small views, or deeply nested views with shadows.","why":"Correct. That’s native rendering work, which shows up on the UI thread."},{"text":"A slow network request.","why":"Waiting on the network doesn’t consume frames on either thread."}],"answer":1},{"q":"

Which test is written the way React Native Testing Library recommends?

","options":[{"text":"Snapshot the rendered tree and update the snapshot whenever it changes.","why":"Snapshots record whatever renders, including bugs, and break on harmless changes."},{"text":"Assert that the component’s internal setDraft was called with a specific object.","why":"That tests implementation, so refactors break it even when behaviour is correct."},{"text":"Find the input by its testID input-2 and read its props.value.","why":"It works, but it doesn’t reflect what users see and misses accessibility problems."},{"text":"Type into the field labelled “Distance (km)”, press the “Save” button by role, and expect onSave to receive 8.4.","why":"Correct. It exercises the component the way a user (and a screen reader) does."}],"answer":3},{"q":"

Your preview build works, but the production build crashes on launch with a missing environment variable. What does this tell you?

","options":[{"text":"Production builds can differ from development and preview; always install and test the actual release build before submitting.","why":"Correct. Build profiles can set different environment variables, and release builds have no Metro to fall back on."},{"text":"EAS Build is unreliable and you should build locally.","why":"Building locally with the same configuration would crash the same way."},{"text":"The stores modified the binary during upload.","why":"Stores don’t change your JavaScript or environment."}],"answer":0},{"q":"

You publish a JavaScript fix with eas update --channel production, but users on builds made from the preview profile don’t receive it. Why?

","options":[{"text":"Updates take a week to propagate.","why":"Updates are available within minutes; the issue is targeting."},{"text":"Preview builds can’t receive updates at all.","why":"They can, on their own channel."},{"text":"Preview builds listen to the preview channel, so they only get updates published there.","why":"Correct. Each build profile’s channel decides which updates it receives."},{"text":"The runtime version must be raised for every update.","why":"Raising it would make the update skip existing builds, not reach more of them."}],"answer":2},{"q":"

Trailhead 1.3 adds a native module. What’s the right way to get it to users?

","options":[{"text":"Publish an eas update to production; users will download the module.","why":"Updates can’t deliver native code."},{"text":"Publish an update and ask users to restart twice.","why":"Restarting doesn’t compile native code into the app."},{"text":"Keep the same version so existing updates still apply.","why":"Then old builds could receive JavaScript calling a module they lack."},{"text":"Raise version, make a production build, submit it for review and release it; updates for 1.3 then target the new runtime version.","why":"Correct. Native changes always travel in a new binary."}],"answer":3}]},"final":[{"q":"

Which description of Trailhead’s architecture is accurate?

","options":[{"text":"React components render HTML that a WebView displays.","why":"React Native has no HTML or WebView in the rendering path."},{"text":"Swift and Kotlin code is generated from your JSX at build time.","why":"Your JSX is not translated into Swift or Kotlin; it runs as JavaScript."},{"text":"JavaScript runs on the UI thread and draws directly to the screen.","why":"JavaScript runs on its own thread; the UI thread draws native views."},{"text":"JavaScript runs in Hermes on its own thread, and the Fabric renderer creates native views that the UI thread draws.","why":"Correct. That’s the New Architecture pipeline every current React Native app uses."}],"answer":3},{"q":"

A new hike card looks squashed: the title overflows and pushes the date badge off screen. The row is flexDirection: 'row'. Which change is idiomatic?

","options":[{"text":"Give the title width: 200.","why":"A fixed width breaks on other screen sizes and with larger text."},{"text":"Give the badge position: 'absolute'.","why":"Taking the badge out of the flow lets the title run underneath it."},{"text":"Give the title’s container flex: 1 and the Text numberOfLines={1}.","why":"Correct. The container absorbs the leftover width and long titles truncate."},{"text":"Switch the row to flexDirection: 'column'.","why":"That changes the design instead of fixing the overflow."}],"answer":2},{"q":"

Which list setup is right for 1,000 hikes grouped by month with sticky headers?

","options":[{"text":"A ScrollView with nested .map() calls for months and hikes.","why":"It renders every row at once, which is slow and memory-hungry."},{"text":"A SectionList with sections shaped { title, data } and a keyExtractor returning each hike’s id.","why":"Correct. It virtualizes rows and renders sticky section headers."},{"text":"One FlatList per month inside a ScrollView.","why":"Nesting virtualized lists in a ScrollView defeats virtualization and triggers a warning."}],"answer":1},{"q":"

Trailhead’s Stats tab is part of a (tabs) group, and hikes/[id] is in the root Stack. A user on Stats opens a hike and swipes back. Where do they land?

","options":[{"text":"On the Stats tab, with its scroll position intact.","why":"Correct. The detail screen was pushed over the tabs; popping it reveals the tab they came from, still mounted."},{"text":"On the first tab, because the tab group resets.","why":"Tabs keep their state; nothing resets on back."},{"text":"On the sign-in screen.","why":"Back pops one screen; it doesn’t leave the protected area."},{"text":"Nowhere; detail screens in the root Stack can’t be swiped back.","why":"Stack screens support the back gesture by default."}],"answer":0},{"q":"

What is the main reason Trailhead keeps parsing and validation in pure functions like parseDistanceKm and validateHikeForm?

","options":[{"text":"Pure functions run on the UI thread, so they’re faster.","why":"They run on the JS thread like everything else in your app code."},{"text":"React Native requires validation to live outside components.","why":"There’s no such requirement; it’s a design choice."},{"text":"They can be tested in milliseconds with plain Jest, without devices, mocks or rendering.","why":"Correct. On mobile, a fast test loop saves far more time than on the web."},{"text":"They make the JavaScript bundle smaller.","why":"Bundle size barely changes; the payoff is testability and clarity."}],"answer":2},{"q":"

A deep link opens trailhead://hikes/9999, but that hike doesn’t exist. What should happen?

","options":[{"text":"The app crashes, which is acceptable for invalid links.","why":"Any link from anywhere can open your app; a crash is never acceptable."},{"text":"The detail screen shows a clear “hike not found” message with a way back to the log.","why":"Correct. Treat deep links as untrusted input and design the not-found state."},{"text":"Expo Router silently redirects to +not-found.tsx because the id is unknown.","why":"The router only matches the URL shape; it doesn’t know which ids exist in your data."}],"answer":1},{"q":"

Trailhead must remember the sign-in token, 600 hikes, and the user’s preferred units. Which mapping is right?

","options":[{"text":"All three in AsyncStorage under separate keys.","why":"The token would be unencrypted, and the hikes would be slow to query."},{"text":"All three in expo-secure-store.","why":"SecureStore is designed for small secrets, not a 600-record log."},{"text":"Token in SQLite, hikes in AsyncStorage, units in SecureStore.","why":"Each item is in the store least suited to it."},{"text":"Token in expo-secure-store, hikes in expo-sqlite, units in AsyncStorage.","why":"Correct. Secrets encrypted, records queryable, preferences simple."}],"answer":3},{"q":"

When is the best moment for Trailhead to ask for camera permission?

","options":[{"text":"On first launch, together with location and notifications, to get it over with.","why":"Users deny what they don’t understand, and on iOS the first denial is hard to undo."},{"text":"Never; expo-image-picker doesn’t need permission for the camera.","why":"Launching the camera always requires the camera permission."},{"text":"When the user taps “Take photo” on a hike, after a short explanation if needed.","why":"Correct. The reason is obvious at that moment, so people say yes."},{"text":"After the user has logged ten hikes, as a reward.","why":"Asking at an unrelated moment is as confusing as asking at launch."}],"answer":2},{"q":"

A tracking screen starts watchPositionAsync in an effect. Which cleanup is correct?

","options":[{"text":"Store the subscription and call subscription.remove() in the effect’s cleanup, handling the case where it arrives after unmount.","why":"Correct. Otherwise GPS keeps running and draining the battery after the screen closes."},{"text":"Call Location.stopAllAsync() when the app goes to the background.","why":"That function doesn’t exist; you remove the subscription you created."},{"text":"No cleanup is needed; React Native stops native subscriptions on unmount.","why":"Native subscriptions don’t know about your components."}],"answer":0},{"q":"

You need to know which components re-render while scrolling Trailhead’s log. Which tool answers that directly?

","options":[{"text":"LogBox","why":"LogBox shows errors and warnings, not render activity."},{"text":"The Profiler in React Native DevTools, recording why each component rendered.","why":"Correct. It shows what rendered, how long it took and what changed."},{"text":"The Xcode console","why":"It shows native logs; it knows nothing about React renders."},{"text":"eas build --profile development","why":"That builds an app; it doesn’t inspect one."}],"answer":1},{"q":"

Which sequence ships Trailhead’s first version to the App Store?

","options":[{"text":"eas update --channel production, then wait for review.","why":"Updates modify existing installs; they can’t create the first store release."},{"text":"npx expo start --no-dev, then upload the QR code to App Store Connect.","why":"The dev server isn’t a build; stores need a signed binary."},{"text":"eas submit, then eas build --profile production.","why":"You can’t submit a build that doesn’t exist yet."},{"text":"eas build --platform ios --profile production, then eas submit --platform ios, test in TestFlight, then submit for review.","why":"Correct. Build, upload, test the real binary, then review."}],"answer":3},{"q":"

A crash in Trailhead’s comma parsing reaches production. Which response is fastest while staying safe?

","options":[{"text":"Remove the app from the store until a new version passes review.","why":"Removing the app hurts every user for a bug you can fix over the air."},{"text":"Publish the fix directly to production without testing to save time.","why":"An untested update can break more than it fixes, for everyone, quickly."},{"text":"Fix and test it, publish with eas update to the preview channel, verify on a real phone, then publish to production.","why":"Correct. JavaScript-only fixes can ship the same day, with a quick check first."},{"text":"Raise the runtime version so the fix reaches all builds.","why":"A new runtime version would stop the update from reaching existing builds."}],"answer":2}],"glossary":[{"id":"native-view","term":"Native view","definition":"A platform UI element, such as UIView on iOS or android.view.View on Android, that React Native creates and updates from your components instead of rendering HTML.","lesson":"l-rn-1-1"},{"id":"new-architecture","term":"New Architecture","definition":"React Native’s rendering and native-module system built on JSI, the Fabric renderer and TurboModules. It has been the only architecture since React Native 0.82.","lesson":"l-rn-1-1"},{"id":"hermes","term":"Hermes","definition":"The JavaScript engine built for React Native. It runs your app’s JavaScript on its own thread, separate from the UI thread that draws views and receives touches.","lesson":"l-rn-1-1"},{"id":"expo-go","term":"Expo Go","definition":"A store app with a fixed set of native modules that loads your project’s JavaScript from the dev server. Great for learning, but it can’t include custom native code.","lesson":"l-rn-1-2"},{"id":"development-build","term":"Development build","definition":"Your own app binary, with your native modules, identity and configuration, plus dev tools like Fast Refresh. You create one with npx expo run or EAS Build.","lesson":"l-rn-1-2"},{"id":"metro","term":"Metro","definition":"The JavaScript bundler and dev server that npx expo start runs. It serves your code to Expo Go or a development build and powers Fast Refresh.","lesson":"l-rn-1-2"},{"id":"pressable","term":"Pressable","definition":"The core component for anything tappable. It reports presses and long presses, and its style can be a function of the pressed state for instant feedback.","lesson":"l-rn-1-4"},{"id":"hit-slop","term":"hitSlop","definition":"A Pressable prop that enlarges the touch area beyond the visible element, so small icons can still meet the 44-point minimum tap target.","lesson":"l-rn-1-4"},{"id":"style-array","term":"Style array","definition":"A style prop given as an array of style objects. React Native merges it left to right, later keys win, and falsy entries are skipped.","lesson":"l-rn-2-1"},{"id":"density-independent-point","term":"Density-independent point","definition":"The unit behind every unitless number in React Native styles. The platform converts points to physical pixels, so sizes look the same on low- and high-density screens.","lesson":"l-rn-2-1"},{"id":"main-axis","term":"Main axis","definition":"The direction a flex container lays out its children, set by flexDirection. It is vertical by default in React Native, and justifyContent positions children along it.","lesson":"l-rn-2-2"},{"id":"safe-area","term":"Safe area","definition":"The part of the screen not covered by notches, rounded corners, the home indicator or system bars. Screens without headers pad themselves using insets from react-native-safe-area-context.","lesson":"l-rn-2-3"},{"id":"virtualization","term":"Virtualization","definition":"The technique FlatList and SectionList use to mount only the rows near the viewport and replace the rest with empty space, keeping long lists fast and memory-light.","lesson":"l-rn-2-4"},{"id":"key-extractor","term":"keyExtractor","definition":"A FlatList prop that returns a stable, unique key for each item, usually its id, so rows keep the right identity as items are added, removed or reordered.","lesson":"l-rn-2-4"},{"id":"file-based-routing","term":"File-based routing","definition":"Expo Router’s model where every file in src/app is a screen and its path is the URL, with _layout files wrapping sibling routes in a navigator.","lesson":"l-rn-3-1"},{"id":"stack-navigator","term":"Stack navigator","definition":"A navigator that pushes screens on top of each other with native animations and back gestures. Screens underneath stay mounted, keeping their state and scroll position.","lesson":"l-rn-3-1"},{"id":"route-group","term":"Route group","definition":"A folder whose name is in parentheses, like (tabs). It shares a layout among its routes without adding a segment to their URLs.","lesson":"l-rn-3-2"},{"id":"dynamic-route","term":"Dynamic route","definition":"A route file named with square brackets, like [id].tsx, that matches any single URL segment and exposes it as a string param through useLocalSearchParams.","lesson":"l-rn-3-2"},{"id":"protected-route","term":"Protected route","definition":"A route wrapped in Stack.Protected with a guard condition. While the guard is false the route is unavailable, and navigation to it, including from deep links, is redirected.","lesson":"l-rn-3-5"},{"id":"deep-link","term":"Deep link","definition":"A URL, such as trailhead://hikes/42, that opens the app directly on a specific screen. Expo Router maps it to a route file automatically.","lesson":"l-rn-3-5"},{"id":"async-storage","term":"AsyncStorage","definition":"An asynchronous, unencrypted key-value store for strings. It suits small preferences, not secrets or large collections of records you need to query.","lesson":"l-rn-4-2"},{"id":"secure-store","term":"SecureStore","definition":"The expo-secure-store module, which encrypts small values such as tokens using the iOS Keychain and the Android Keystore.","lesson":"l-rn-4-2"},{"id":"migration","term":"Database migration","definition":"A versioned step that upgrades an existing database schema, such as adding a column, run once per device in order, typically tracked with PRAGMA user_version in SQLite.","lesson":"l-rn-4-2"},{"id":"config-plugin","term":"Config plugin","definition":"An app.json entry that writes native configuration, such as iOS permission descriptions or Android manifest entries, when the app is built. Changes need a new build.","lesson":"l-rn-4-3"},{"id":"can-ask-again","term":"canAskAgain","definition":"A field in an Expo permission response. When false, the system won’t show the permission prompt again, so only the Settings app can change the user’s answer.","lesson":"l-rn-4-3"},{"id":"react-native-devtools","term":"React Native DevTools","definition":"The built-in debugger, opened with j in the Metro terminal, offering a console, breakpoints, a Components inspector and a Profiler for your running app.","lesson":"l-rn-5-1"},{"id":"jest-expo","term":"jest-expo","definition":"A Jest preset that configures transforms for React Native and mocks the native side of Expo modules, so tests run in Node without a device.","lesson":"l-rn-5-2"},{"id":"eas-build","term":"EAS Build","definition":"Expo’s cloud service that compiles and signs Android and iOS binaries from your project using profiles defined in eas.json, such as development, preview and production.","lesson":"l-rn-5-3"},{"id":"eas-update","term":"EAS Update","definition":"Expo’s service for publishing new JavaScript and assets to installed builds over the air, without a store release. It can’t deliver native code changes.","lesson":"l-rn-5-4"},{"id":"runtime-version","term":"Runtime version","definition":"A label shared by a build and its compatible updates. An update only applies to builds with the same runtime version, which protects old builds from JavaScript needing newer native code.","lesson":"l-rn-5-4"}]}