ReactJS Tutorial

What Is React? React is a JavaScript library for building user interfaces. It is declarative, component-based, and updates efficiently through the Virtual DOM. Why React? ...

What Is JSX? JSX is a JavaScript syntax extension that looks like HTML but compiles to React.createElement calls. Syntax Rules Single root element (or fragment). Close all tags; ...

Prerequisites Node.js 18+ with npm. Vite is the recommended tool (Create React App is deprecated). Create a Project Project Structure src/ holds components, hooks and services; ...

Functional Components Modern React components are plain functions returning JSX. Names use PascalCase. Composition over Inheritance Build complex UIs from small components and ...

What Are Props? Props are read-only data passed from parent to child - the configuration of a component. Default Props and Validation Provide fallbacks with default parameters and ...

Conditional Rendering Use logical AND and ternaries inside JSX; use early returns for empty or loading states. Rendering Lists Map arrays to elements and always supply a stable ...

Presentational vs Logic Keep UI components focused on rendering; extract logic into custom hooks instead of container components. Compound Components Related components share ...

Styling Options Tailwind - utility-first, responsive and dark mode built in. CSS Modules - scoped class names with zero deps. Bootstrap - fast admin and CRUD UIs. Dark Mode Toggle ...

The useState Hook Updating Objects and Arrays Never mutate - spread into new values so React detects the change. State vs Props State is local and mutable via its setter; props ...

React Events Synthetic camelCase events: onClick, onChange, onSubmit. Always call e.preventDefault() in submit handlers. Controlled Components Validation Validate on submit and on ...

The useEffect Hook Run side effects after render. An empty dependency array runs once; listed values re-run the effect when they change. Cleanup and Abort Return a cleanup ...

useRef Holds mutable values and DOM nodes without triggering renders. useMemo and useCallback Memoize expensive values and stable callbacks for optimized children. useReducer ...

Setup Routes and Navigation Map URLs to components with Routes and Route; navigate with Link, NavLink and useNavigate. Params and Nesting Read :id with useParams, ?q= with ...

Creating Context Auth and Theme Providers Provide user/login/logout and theme/toggle at the app root; consume anywhere below. Context vs Props vs Redux Props for 1-2 levels; ...

Core Flow UI dispatches actions; reducers update the store; components read with useSelector. Slice and Store createSlice bundles state, reducers and actions; configureStore ...

RTK Query Declares endpoints with caching, deduping and tag invalidation - replacing most hand-written thunks. Auth Headers Attach Bearer tokens in prepareHeaders; invalidate tags ...

Code Splitting Lazy-load routes and heavy components inside Suspense with a loading fallback. Error Boundaries Class-only components catching render errors; show fallback UI with ...

Approaches Tailwind for speed, responsive and dark mode. CSS Modules for scoped styles. Bootstrap for quick admin UIs. Responsive and Dark Mode Use sm/md/lg prefixes; persist ...

TypeScript with React Type props with interfaces, state with generics, events with React types, and API responses with Promise types. JWT Flow Login returns access plus refresh ...

Unit Tests Vitest plus Testing Library: render, query by role, fire events, assert visible behavior. Mocking APIs Spy on fetch or use MSW; cover loading, success and error states. ...

Measure First Profile with React DevTools before optimizing; colocate state to shrink render scope. Memoization memo skips unchanged children; useMemo caches values; useCallback ...

Architecture React UI, component, custom hook, API service, REST API, Spring Boot or Grails, database. API Layer Centralize base URL, auth headers, 401 refresh, retries and typed ...

Production Build Nginx SPA Hosting Serve dist/ with try_files fallback to index.html and proxy /api to the backend. Docker and CI/CD Multi-stage build: node builds, nginx serves. ...

Student Management Login, dashboard, student CRUD, search, pagination and reports on a Spring/Grails plus PostgreSQL API. E-Commerce and Job Portal Cart and checkout with Redux; ...

Beginner What is React and JSX? Props vs state? Virtual DOM? Keys? Controlled vs uncontrolled? useState, useEffect, Context, Router basics. Intermediate useMemo vs useCallback? ...