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Q2 ReactJs

To render a React component to the DOM, import React and ReactDOM, select a root HTML element, and use root.render to display the component. Running 'npm start' initiates the development server, compiles the code, and injects the React app into the HTML. The journey from package.json to index.html involves reading dependencies, compiling code, and dynamically injecting the JavaScript bundle to display the UI in the browser.

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38 views2 pages

Q2 ReactJs

To render a React component to the DOM, import React and ReactDOM, select a root HTML element, and use root.render to display the component. Running 'npm start' initiates the development server, compiles the code, and injects the React app into the HTML. The journey from package.json to index.html involves reading dependencies, compiling code, and dynamically injecting the JavaScript bundle to display the UI in the browser.

Uploaded by

ranjeetphalke.rmdssoe.mech
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
Available Formats
Download as PDF, TXT or read online on Scribd
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Q1. How do you render a React component to the DOM?

To render a React component to the DOM, follow these steps:

1. Import React and ReactDOM:

import React from 'react';

import ReactDOM from 'react-dom/client';

import App from './App';

2. Select the root element in your HTML where the React app will be injected:

const root = ReactDOM.createRoot(document.getElementById('root'));

3. Render the React component inside the root:

root.render(<App />);

4. The component <App /> and all its child components will now be displayed inside the #root
element of index.html.

Q2. What happens once we type npm start?

When you run npm start, the following steps occur:

1. Reads package.json – Looks for the scripts section where "start" is defined.
2. Runs react-scripts start – This starts the development server (webpack-dev-server).
3. Loads webpack.config.js – Webpack compiles JavaScript, JSX, and CSS files.
4. Starts Babel transpilation – Converts modern JavaScript (ES6+) and JSX into browser-
compatible JS.
5. Creates an in-memory bundle – Webpack serves the bundled code from memory for fast
development.
6. Starts a development server – A local server (usually http://localhost:3000) is started.
7. Injects JavaScript into index.html – The bundled React app is injected into the <div
id="root"></div>.
8. Hot Module Replacement (HMR) is enabled – Any code changes are reflected without a full
page reload.
Q3. Journey from package.json to index.html in points
1. Reads package.json – Finds dependencies and scripts (like start).
2. Executes npm start – Runs react-scripts start, which sets up Webpack.
3. Webpack compiles code – Transpiles JSX and modern JavaScript using Babel.
4. Processes assets – CSS, images, and static files are bundled.
5. Creates a virtual bundle – Webpack does not generate physical files but keeps them in
memory.
6. Loads public/index.html – The development server serves this HTML file.
7. Injects JavaScript bundle – A <script> tag pointing to the compiled JS is inserted
dynamically.
8. Executes index.js – This is the entry point that renders React components inside #root.
9. Displays UI in browser – React updates the Virtual DOM, and changes reflect in the browser.
10. Enables Hot Module Replacement (HMR) – React updates components without reloading the
entire page.

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