element with an id of root. This root element acts as a placeholder where your React components will be rendered.

The Role of index.js

The index.js file is the entry point for your React application logic. It is responsible for rendering your React components into the root element defined in the index.html file.

Inside the index.js file, you’ll typically find code that imports the necessary dependencies and renders the root component of your application using the ReactDOM.render() method. This method takes two arguments: the component you want to render and the DOM element where it should be rendered.

import React from 'react';
import ReactDOM from 'react-dom';
import App from './App';

ReactDOM.render(
  
    
  ,
  document.getElementById('root')
);

The Connection

The connection between index.html and index.js happens through the ReactDOM.render() method in the index.js file. When the browser loads the index.html file, it encounters the

element. Then, when the ReactDOM.render() method is called, it finds the root element by its ID and replaces its content with the rendered React components.

This connection allows your React components to be dynamically rendered and updated in the browser as your application state changes.

Conclusion

In a Create-React-App application, the index.html file serves as the main HTML entry point, providing a placeholder root element. The index.js file, on the other hand, is responsible for rendering your React components into the root element using the ReactDOM.render() method. This connection between the two files allows your React application to come to life and be displayed in the browser.

Now that you understand the connection between index.html and index.js, you’re ready to dive deeper into React development and build amazing applications!