📘 React.js Notes — Beginner to Advanced

A complete collection of React.js notes, covering everything from beginner fundamentals to advanced concepts.
Includes definitions, explanations, examples, best practices, and real-world interview questions.

Perfect for beginners, students, and developers preparing for interviews.

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🚀 Topics Covered

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✅ 1. Introduction to React

• What is React?

• Why React?

• SPA (Single Page Application)

• Virtual DOM & Reconciliation

• JSX (JavaScript XML)

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✅ 2. Installing & Setting Up React

• Installing Node.js

• Create React App (CRA)

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✅ 3. Components

• Function Components

• Class Components

• Component Structure

• Props (Passing Data)

• State (useState / setState)

• Controlled vs Uncontrolled Components

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✅ 4. React Hooks

• useState

• useEffect

• useRef

• useContext

• useMemo

• useCallback

• Custom Hooks

• Lifecycle Equivalents Using Hooks

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✅ 5. Higher Order Components (HOC)

• What is HOC?

• Why We Use It?

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✅ 6. React Router

• What is Client-Side Routing?

• Installing React Router

• createBrowserRouter

• RouterProvider

• Link, Outlet

• useNavigate, useParams, useLocation

• Nested Routes

• Error Handling (useRouteError)

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✅ 7. State Management (Redux & Toolkit)

• Why Redux?

• Redux Store

• Reducers

• Actions & action.payload

• Slice (createSlice)

• Dispatch & Selectors

• Provider Setup

• Counter Example (Beginner Friendly)

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✅ 8. Lists & Rendering

• map() Usage in React

• Conditional Rendering

• Filter & Search Functions

• Keys in Lists (Why They Matter)

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✅ 9. Tailwind CSS

• Installing Tailwind in React

• Utility Classes

• Responsive Design

• Tailwind Components

• Shimmer UI (Skeleton Loading)

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✅ 10. Optimization & Advanced Topics

• Memoization

• Lazy Loading

• Code Splitting

• Error Boundaries

• Debouncing & Throttling

• Custom Hooks — Best Practices

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🧑‍💻 Technologies Used

• React.js
• JavaScript (ES6+)
• Tailwind CSS
• React Router
• Redux Toolkit
• NPM

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