modify the index.js

 src/index.js

import React from 'react';

import ReactDOM from 'react-dom/client';

import './index.css';

import App from './App';

import reportWebVitals from './reportWebVitals';

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

root.render(

  <React.StrictMode>

    <App />

  </React.StrictMode>

);

// If you want to start measuring performance in your app, pass a function

// to log results (for example: reportWebVitals(console.log))

// or send to an analytics endpoint. Learn more: https://bit.ly/CRA-vitals

reportWebVitals();

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import React from 'react';

import ReactDOM from 'react-dom/client';

const myFirstElement = <h1>Hello React!</h1>

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

root.render(myFirstElement);

=

import React from 'react';

import ReactDOM from 'react-dom/client';

const myelement = (

  <table>

    <tr>

      <th>Name</th>

    </tr>

    <tr>

      <td>John</td>

    </tr>

    <tr>

      <td>Elsa</td>

    </tr>

  </table>

);

const container = document.getElementById('root');

const root = ReactDOM.createRoot(container);

root.render(myelement);

=

index.html

 <div id="root"></div>

because of that we can call id is root

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