React Reference

Getting Started with React — what React is, the virtual DOM and reconciliation, what is new in React 19, and creating an app with a framework or with Vite.

JSX and Rendering — JSX syntax, embedding expressions with curly braces, conditional rendering, rendering lists with keys, and mounting a tree with createRoot.

Components and Props — function components, passing and reading props, children, one-way data flow, composition over inheritance, and keeping components pure.

State and Events — event handlers and the SyntheticEvent, useState, the render/commit cycle, batching and updater functions, and immutable object/array updates.

Core Hooks and the Rules of Hooks — the Rules of Hooks, useState vs. useReducer, useRef and useId, and a reference table of every built-in Hook.

Effects and Lifecycle — useEffect, dependency arrays and cleanup, fetching with a race guard, "you might not need an Effect", useEffectEvent, and useLayoutEffect.

Custom Hooks — extracting stateful logic into use* functions, and worked examples (useToggle, useLocalStorage, useDebounce, useFetch, useOnlineStatus).

State Management — lifting state up, controlled vs. uncontrolled inputs, structuring state, Context, the reducer + context pattern, and third-party libraries.

Performance and Concurrent Features — measuring re-renders, memo / useMemo / useCallback, the React Compiler, useTransition and useDeferredValue.

Code Splitting and Suspense — lazy + <Suspense>, route-based splitting, Suspense for data and the use API, and error boundaries.

Forms and Actions — controlled inputs, and the React 19 Actions model with useActionState, useFormStatus, and useOptimistic.

Routing — a brief orientation: React ships no router; the options, and minimal React Router examples.

Data Fetching — fetch in an Effect and its problems, axios, TanStack Query / SWR, GraphQL clients, and framework data loading.

Refs and the DOM — useRef for non-rendering values, DOM refs, ref as a prop in React 19, useImperativeHandle, and flushSync.

TypeScript with React — typing props, children, hooks, and events; generic components and utility types; and the removal of PropTypes in React 19.

Testing — the test pyramid, Jest / Vitest setup, React Testing Library and act(), mocking the network with MSW, testing Hooks, and end-to-end tests with Playwright and Cypress.

Server Rendering, SSG and React Server Components — CSR/SSR/SSG/ISR, hydration, react-dom/server and streaming, RSC and Server Functions, and an SEO-friendly e-commerce example.

Build and Deployment — what a bundler does, building with Vite, the three deployment models, and a worked Vite SPA on AWS S3 + CloudFront.

Styling and UI Libraries — CSS Modules, Tailwind, CSS-in-JS, component libraries (MUI, Ant Design, Chakra UI, PrimeReact, gluestack, Radix), and accessibility of interactive components.

The Rules of React — purity and idempotency, no side effects in render, immutable props and state, letting React call your components and Hooks, and the Rules of Hooks.

Cheat sheet — a one-page, downloadable PDF summary of the essentials above for quick memorization.