Mobile development cheat sheet (React Native)

1. 1JavaScript and TypeScript essentialsThe JavaScript and TypeScript that React Native code depends on: types, nullish values, immutable updates, closures and async code.7 concepts

   1. 1Types, interfaces and unionsTypeScript adds static types to JavaScript.
   2. 2Optional chaining and nullish coalescinga?.b returns undefined instead of throwing when a is null or undefined.
   3. 3Immutable updates with spreadInstead of changing an array or object in place, you create a new one with the spread operator ..., map or filter.
   4. 4Closures and stale valuesA closure is a function that remembers the variables from where it was created.
   5. 5Promises and async/awaitA Promise represents a result that arrives later.
   6. 6Discriminated unionsA union of object types that share one literal field, such as status.
   7. 7Modules and npmEach file is a module that uses import and export.

   7 in this chapterOpen this chapter
2. 2UI and layoutTurning a design into screens: small composable pieces, layout containers, long lists, forms, theming and fitting every screen size.10 concepts

   1. 1Declarative UIYou describe what the screen should look like for the current state, and the framework works out what to change on screen.
   2. 2Core componentsReact Native renders real native views.
   3. 3Flexbox and StyleSheetLayout uses Flexbox, like CSS, with numbers in density-independent pixels.
   4. 4Rows, columns and stacksThe basic layout containers place children horizontally, vertically or on top of each other, with spacing and alignment options.
   5. 5Lazy listsA lazy list only builds the rows currently on screen, plus a few ahead, and recycles them as you scroll.
   6. 6Text input and formsA text field shows a value from state and reports every change back.
   7. 7Theming and dark modeA theme defines colours, typography and shapes in one place.
   8. 8Platform design guidelinesMaterial Design 3 is Google's design system for Android, and the Human Interface Guidelines are Apple's rules for iOS.
   9. 9Safe areas and screen sizesSafe areas, or insets, are the parts of the screen not covered by the notch, status bar, camera cutout or gesture bar.
   10. 10Hot reload and previewsTools that show code changes in a running app or an editor preview within a second or two, without rebuilding the whole app.

   10 in this chapterOpen this chapter
3. State and navigationWhere state lives, how screens share it and how users move between screens, including tabs, sheets and deep links.9 conceptsOpens with credits
4. Networking and local dataCalling APIs, storing data on the device and keeping the app useful on a slow or missing connection, with tokens kept safe.10 conceptsOpens with credits
5. Device features and notificationsWhat makes a phone a phone: the app lifecycle, permissions, camera, location, notifications, background work and calling native code.9 conceptsOpens with credits
6. Testing, performance and accessibilityProving the app works and keeps working: unit and UI tests, profiling a release build, accessibility with real screen readers and a security check.10 conceptsOpens with credits
7. Publishing and releasesGetting the app to real users: IDs and versions, release builds and signing, beta testing, privacy declarations, store review, crash reporting and rollouts.13 conceptsOpens with credits
8. 8Glossary, A to ZEvery concept in the sheet and the smaller terms it uses, in one list.153 terms

Apps for Android and iOS.