149 docs tagged with "middle"

VoiceOver and TalkBack, accessibility props and their aria-* forms, grouping and hiding, focus and announcements, font scaling, touch targets, reduce motion, testing

Big O, Omega and Theta, complexity classes, abstract data types, arrays, linked lists, stacks, queues, hash tables, trees, heaps, graphs, sorting, search and common algorithmic techniques

Animated values, timing / spring / decay, interpolate, composition, the native driver, LayoutAnimation, why not to animate with setState

AppState states and events, refresh on return, hiding content in the app switcher, why JS stops in the background, expo-background-task, Headless JS, foreground services

File conventions of the app/ directory, segments, route groups, parallel and intercepting routes

Array methods by group, mutating and non-mutating, common pitfalls

Authentication vs authorization, sessions vs JWT, OAuth and OIDC

Sessions in cookies, Data Access Layer, Proxy, protecting Server Actions

OAuth and OIDC in the system browser, expo-auth-session and react-native-app-auth, native Apple and Google sign-in, token lifecycle and refresh, biometric login

Naming, DRY / KISS / YAGNI and when DRY hurts, Clean Code principles, code smells

bind(), call(), apply()

Content, padding, border and margin, box-sizing, margin collapsing, block vs inline, block formatting context, overflow, logical properties

Gitflow, GitHub Flow and trunk-based development, which one to choose

Cookies vs localStorage vs sessionStorage, cookie attributes and security

Bundle analysis, tree shaking, code splitting and lighter imports

exec, execFile, spawn and fork, buffered vs streamed output, shell injection, IPC with fork

CI vs continuous delivery vs continuous deployment, pipeline stages, caching, preview environments, a GitHub Actions example, CI/CD for mobile apps

Legacy class components, lifecycle methods and their hook equivalents

Class syntax, inheritance, private fields and static methods

'use client' as a boundary, Server Components as children, serializable props, context providers

A function that remembers the variables of the scope it was created in

Why code review exists, what to look at, how to give and receive feedback

An index of live-coding tasks - bind, call/apply, Promise.all, debounce, deep copy, memoize, flat, event emitter, LRU cache - and where each is solved

Composition, conditional rendering, compound components, render props and HOCs

Transitions, useDeferredValue, Suspense and use

Content-Security-Policy header, directives and source values, strict CSP with nonces and strict-dynamic, Report-Only, frame-ancestors

LCP, INP and CLS, thresholds, field vs lab data, how to improve each metric

Same-Origin Policy, what an origin is, preflight and credentials

The critical rendering path, render-blocking resources, resource hints and fetchpriority, images, fonts, compression and caching

How CSRF works, why CORS does not stop it, SameSite cookies, CSRF tokens, Origin and Fetch Metadata checks

Stored, reflected and DOM-based XSS, escaping by context, sanitization, XSS in React, Trusted Types

CSS variables, var() with a fallback, cascade and inheritance, invalid at computed-value time, @property, theming with light-dark() and color-mix(), vs Sass variables

Tracks and fr, repeat() with auto-fill vs auto-fit, line placement and grid areas, implicit grid, subgrid, Grid vs Flexbox

Transitions vs keyframe animations, why to animate transform and opacity, will-change, CSS vs JavaScript animations, reduced motion

getStaticProps, getStaticPaths, getServerSideProps, ISR and on-demand revalidation, client-side fetching

Fetching in Server Components, waterfalls, parallel requests, streaming, preload, passing a promise to the client

What data types exist in modern JS

Debounce vs throttle, where to use each, an implementation of both and how to use them in React

React Native DevTools and its panels, LogBox, native logs from Xcode and logcat, crash reporting in production with source maps

Console, breakpoints, DevTools panels, React and Redux DevTools

Custom URL schemes vs Universal Links and App Links, linking config, cold start vs a running app, opening a screen from a notification

Creational, structural and behavioral design patterns with frontend examples, Observer vs Pub/Sub, Factory Method vs Simple Factory

Capturing and bubbling, target vs currentTarget, delegation, listener options

Numeric, string and const enums, and why unions often replace them

Environment variables in React Native and Expo, why values in the JS bundle are not secret, where to keep real secrets

NEXT_PUBLIC_ variables inlined at build time vs server variables read at runtime, .env file order, one Docker image for several environments

What error boundaries catch and what they don't, where to place them, how to reset them and react-error-boundary

throw, try...catch...finally, custom errors and errors in async code

Operational vs programmer errors, system errors and codes, error handling in callbacks, promises and EventEmitter, unhandled errors, Express middleware

import and export, live bindings, modules in the browser, dynamic import, top-level await, import maps and import attributes

Call stack, tasks and microtasks, and the order of execution

libuv event loop phases, process.nextTick and microtasks, setImmediate vs setTimeout, timers in Node.js

EventEmitter, synchronous listeners, the special error event, once and promises, listener leaks, EventEmitter vs EventTarget

What the engine creates to run code, hoisting and the scope chain

What fastlane automates for iOS and Android releases, lanes, match, fastlane vs EAS

Main and cross axes, container and item properties, flex-grow / shrink / basis and flex 1, gap and wrapping, the min-width trap, order

Pure functions, side effects, referential transparency, immutability, higher-order functions, closures, currying vs partial application, composition, functors and monads

Function Declarations, Function Expressions, and Arrow Functions

How memory is freed in JavaScript and where leaks come from

Type parameters, constraints, defaults and generic React components

Gesture Responder System, Pressable, PanResponder, React Native Gesture Handler and gesture composition

pushState and replaceState, the popstate event, hash vs history routing, and the Navigation API

Built-in hooks at a glance, the Rules of Hooks and custom hooks

From a URL to pixels - DNS, connection, parsing, the rendering pipeline

Methods, status codes, caching, HTTP versions and requests with fetch

Creating an HTTP server with node:http, request and response as streams, reading the body, headers, making requests with fetch

What an index is, B-tree and other index types, composite, partial and expression indexes, when an index is not used, EXPLAIN

IntersectionObserver, ResizeObserver and MutationObserver, when their callbacks run, lazy loading, infinite scroll and the ResizeObserver loop error

The iteration protocols, generator functions, iterator helpers and async iteration

KeyboardAvoidingView per platform, Android adjustResize / adjustPan, keyboardShouldPersistTaps, Keyboard API, react-native-keyboard-controller, moving to the next field

Rendering only the visible part of a long list or grid

Rendering lists with map, choosing a key, an index as a key, resetting state with a key

ScrollView vs FlatList vs SectionList vs FlashList, virtualization, FlatList optimization props

Map vs plain objects, Set and set methods, WeakMap and WeakSet and when to use them

Merge vs rebase, fast-forward and merge commits, squash, interactive rebase, cherry-pick and conflicts

Metadata API (metadata vs generateMetadata, merging, title templates), OG images, sitemap and robots, viewport, streaming metadata

Threat model of a mobile app, OWASP MASVS and Mobile Top 10, what the bundle reveals, HTTPS and SSL pinning, root detection vs attestation, sensitive data on screen and in logs, WebView

CommonJS vs ES modules in Node.js, how Node.js picks the module type, require(esm), module.exports vs exports, resolution and caching

Link and prefetching, useRouter, usePathname, useSearchParams, redirect and where to redirect

React Navigation vs Expo Router, stack / tabs / drawer, screens that stay mounted, navigate vs push vs popTo, typed params, auth flow

NoSQL data models (key-value, document, wide-column, graph), SQL vs NoSQL, transactions and consistency, CAP theorem, when to choose which

Cloning objects, accessing properties, iterating, Object static methods

NetInfo and expo-network, isConnected vs isInternetReachable, cached reads, queued writes, offline-first, TanStack Query onlineManager and focusManager, conflicts and idempotent requests

Encapsulation, inheritance, polymorphism and abstraction with TypeScript examples, composition over inheritance

Code splitting and next/dynamic, next/image, next/font, next/script

When to optimize, component structure, memo, useMemo, useCallback and React Compiler

What over-the-air updates can change without the store, EAS Update, runtime versions, what happened to CodePush, store rules

npm, pnpm, Yarn and Bun, lockfiles, semver ranges, dependency types, workspaces, Corepack, install scripts

Why a React Native app lags, the frame budget of the JS and UI threads, measuring in release builds, common causes and fixes, startup time

Runtime permissions on iOS and Android, permission statuses, blocked permissions and settings, libraries

createPortal, event bubbling through portals, modal accessibility

position values, containing block, why sticky does not stick, stacking context and z-index, top layer, anchor positioning, ways to center an element

Imperative vs declarative programming, with examples in JavaScript

Promise states and chaining, Promise.all vs allSettled vs race vs any, async/await, errors and cancellation

The prototype chain, __proto__ vs prototype, what new does

What Proxy (formerly Middleware) is, where it runs in a request, matcher, NextResponse, what it is for and not for

Publishing to the App Store and Google Play, signing, provisioning profiles, Play App Signing, test tracks, review and staged rollout

How push notifications work, device tokens, notification vs data messages, foreground / background / quit behavior, APNs keys, libraries

createContext, providers, useContext and use, re-renders of consumers

createRoot, hydrateRoot, hydration, StrictMode and flushSync

Legacy bridge vs New Architecture (JSI, Fabric, TurboModules, Codegen), threads, rendering pipeline, native libraries and autolinking

React Router modes, nested routes, navigation hooks, loaders and protected routes

Polling, long polling, Server-Sent Events and WebSocket, how each works and when to choose it

Reanimated 4 shared values, worklets and the UI thread, animated styles, layout animations, CSS animations, why it is faster than Animated

Store, actions and reducers, Redux Toolkit slices, React Redux hooks and memoized selectors

useRef, DOM refs, callback refs, ref as a prop and useImperativeHandle

Creating regular expressions, flags, methods and basic syntax

One-to-one, one-to-many and many-to-many relationships, how each is built with foreign keys, junction tables, querying with JOIN

Render and commit phases, virtual DOM, diffing heuristics and Fiber

SSG, ISR, SSR and CSR in the Pages Router, automatic static optimization

When rAF and idle callbacks run in a frame, scheduler.yield() and postTask, which one to use for animation, background work and long tasks

Mobile-first media queries and range syntax, CSS units, clamp() / min() / max(), container queries, srcset and sizes vs picture, user preference queries

REST vs GraphQL - over- and under-fetching, caching, errors, N+1, versioning, and where tRPC fits

route.ts, HTTP methods, dynamic segments, Route Handler vs Server Action

Insets for the notch, status bar and navigation bar, react-native-safe-area-context, edge-to-edge on Android 15+, navigators and insets

'use server', forms and useActionState, validation, revalidation, why an action is a public endpoint

RSC vs SSR, what Server Components can't do, static and dynamic rendering, streaming, hydration

Server state with TanStack Query, query keys, staleTime and gcTime, mutations, invalidation and optimistic updates

Service worker as a network proxy, registration and scope, lifecycle and updates, caching strategies, offline and PWA

useEffect dependencies, cleanup order, StrictMode, race conditions and useLayoutEffect

Socket.IO vs WebSocket, transports, events and acknowledgements, rooms and namespaces, scaling with adapters

The five SOLID principles with frontend interpretations and TypeScript examples

Cascade order, specificity, :is() / :where() / :has(), nesting, @layer, inheritance and the inherit / initial / unset / revert keywords

useState and useReducer, state as a snapshot, batching, immutable updates

AsyncStorage, MMKV, SecureStore and SQLite, where each kind of data goes on the device, tokens in Keychain / Keystore, persisting app state

Readable, Writable, Duplex and Transform streams, backpressure, pipeline vs pipe, async iteration, stream events

CSS Modules, Tailwind, CSS-in-JS and Sass compared

Event handlers, SyntheticEvent, event delegation on the root and differences from DOM events

Types of tests, pyramid vs trophy, test doubles, coverage, AAA, TDD and BDD, test runners and E2E tools

React Testing Library queries, user-event, async tests and hooks

What the `this` keyword refers to in JavaScript

ACID, BEGIN / COMMIT / ROLLBACK and savepoints, isolation levels and read anomalies, how PostgreSQL actually implements them, lost updates and locking

What strict enables, useful flags beyond strict, new defaults in TypeScript 6 and a config for an app with a bundler

The as syntax, as const, satisfies, non-null assertion and when a type guard is safer

typeof, instanceof, in, equality, discriminated unions, type predicates and assertion functions

keyof, typeof, indexed access, mapped, conditional and template literal types, infer

Declaration merging, extends vs intersection, implicit index signatures and which one to choose

Props, children, events, hooks, context, wrapping native elements and ref as a prop in React 19

Parts of a URL, new URL and URLSearchParams, percent-encoding, encodeURI vs encodeURIComponent

Partial, Required, Readonly, Pick, Omit, Record, Exclude, Extract, NonNullable, ReturnType, Parameters, Awaited and NoInfer

var, let and const, hoisting and the temporal dead zone

WCAG and its levels, semantic HTML, accessible names, keyboard and focus, ARIA rules, contrast, testing

Custom elements, Shadow DOM, templates and slots, what crosses the shadow boundary, Declarative Shadow DOM, forms, Web Components with frameworks

Dedicated and shared workers, postMessage and structured clone, transferable objects, SharedArrayBuffer, when a worker helps

Actions, use, ref as a prop and other changes of React 19 and its minor versions; removed APIs and migration

What makes a component re-render, what does not, why children re-render and how to find the cause

Kinds of state and where each belongs, client vs server state, when a store is needed, Zustand

Worker threads for CPU-heavy work, messaging and shared memory, thread pools, worker_threads vs cluster and child_process

Controlled and uncontrolled inputs, form Actions in React 19, form libraries