Download ReactJS Handwritten Notes

ReactJS has become one of the most widely adopted libraries for building dynamic, high-performance front-end applications. Whether you're a student preparing for exams, a beginner diving into front-end development, or a professional refreshing your fundamentals, ReactJS handwritten notes offer a concise and effective method for mastering the core concepts. In this comprehensive guide, we provide structured, easy-to-understand content that covers all critical React topics in a handwritten-style format, optimized for rapid learning and deep understanding.

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Introduction to ReactJS

ReactJS is a JavaScript library developed by Facebook for building user interfaces, especially for single-page applications. It allows developers to create reusable UI components and manage the state effectively.

Created by: Facebook
Initial Release: 2013
Main Concept: Component-Based Architecture
Language: JavaScript (JSX)

Why Use ReactJS?

Component-Based: Build encapsulated components that manage their own state.
Declarative: Makes code more predictable and easier to debug.
Virtual DOM: Efficient rendering for dynamic web applications.
Unidirectional Data Flow: Enhances debugging and performance.
Reusable Components: Write once, reuse everywhere.

Core Concepts in ReactJS

1. JSX (JavaScript XML)

JSX is a syntax extension for JavaScript. It allows us to write HTML in React.

jsx

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const element = <h1>Hello, world!</h1>;

JSX makes code readable and simplifies UI development.
Babel compiles JSX to React.createElement() calls.

2. Components

Components are the building blocks of a React application. There are two types:

Functional Components

jsx

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function Welcome(props) {

return <h1>Hello, {props.name}</h1>;

}

Class Components

jsx

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class Welcome extends React.Component {

render() {

return <h1>Hello, {this.props.name}</h1>;

}

3. Props (Properties)

Props are read-only attributes used to pass data from parent to child components.

jsx

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Immutable
Accessed via this.props in class components or props in functional components.

4. State in React

State is a built-in object that stores property values that belong to a component.

jsx

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class Counter extends React.Component {

constructor() {

super();

this.state = { count: 0 };

}

Mutable
Use setState() to update the state.

5. Lifecycle Methods

Lifecycle methods allow you to control what happens at specific points in a component’s life.

componentDidMount()
componentDidUpdate()
componentWillUnmount()

6. Event Handling

React normalizes events to maintain consistency across different browsers.

jsx

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<button onClick={this.handleClick}>Click Me</button>

Use camelCase for event handlers.
Pass function references, not function calls.

7. Conditional Rendering

You can render different UI elements based on conditions using:

if-else
ternary operator
logical && operator

jsx

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{isLoggedIn ? <Logout /> : <Login />}

8. Lists and Keys

React uses map() to render lists.

jsx

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const items = numbers.map((number) =>

<li key={number.toString()}>{number}</li>

);

Keys help React identify which items have changed, added, or removed.

9. Forms in React

React uses controlled components for form inputs.

jsx

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Form data is handled by the component’s state.

10. React Hooks (Functional Component Features)

Hooks allow the use of state and lifecycle features in functional components.

useState()
useEffect()
useContext()

Example:

jsx

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const [count, setCount] = useState(0);

useEffect(() => {

document.title = `You clicked ${count} times`;

});

React Router

React Router is used for routing in single-page applications.

bash

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npm install react-router-dom

Example:

jsx

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</Routes>

</BrowserRouter>

Components: BrowserRouter, Routes, Route, Link, NavLink

State Management with Redux

Redux is a predictable state container for JavaScript apps.

Single source of truth
State is read-only
Changes with pure functions

Main Concepts:

Actions
Reducers
Store
Dispatch

Styling in React

React allows multiple ways to style components:

CSS Modules
Styled Components
Inline Styling

jsx

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const style = { color: "blue", fontSize: "18px" };

<h1 style={style}>Hello World</h1>;

React Performance Optimization

Use React.memo for component memoization.
Use useCallback and useMemo hooks.
Avoid unnecessary re-renders with proper key usage and pure components.

ReactJS Interview Notes – Quick Reference

Concept	Description
JSX	JavaScript + XML
Component	Reusable UI Block
State	Mutable local data
Props	Immutable external data
Lifecycle	Component timeline methods
useState	Add state in functional components
useEffect	Side-effects handler
Virtual DOM	Fast UI rendering

ReactJS Project Ideas for Practice

To-Do List App
Weather App using API
E-commerce Shopping Cart
Blog Application
Portfolio Website

Each of these projects strengthens your understanding of components, props, state management, and routing.

Download ReactJS Handwritten Notes (PDF)

If you’re looking for handwritten-style notes for revision or academic use, we recommend creating or downloading handwritten PDFs that summarize each concept neatly. You can create your own note layout including:

Flowcharts of component lifecycle
Tables for Hooks comparison
Diagrams for data flow

These personal notes help reinforce learning and are especially helpful during interviews and exams.

Final Thoughts

Mastering ReactJS doesn't require memorizing every function but understanding how each piece works together — from components to hooks and routing to state management. These ReactJS handwritten notes serve as an all-in-one resource for grasping the full picture of front-end development with React.

Keep practicing, building, and reviewing these handwritten notes for complete mastery of ReactJS.

Download ReactJS Handwritten Notes

📘 Download ReactJS Handwritten Notes

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