React 19 is the latest version of the popular JavaScript library for building user interfaces. It comes with several new features and improvements that make it even more powerful and easier to use.

Concurrent mode

Concurrent mode is a new feature in React 19 that allows you to write code that can run in parallel. This can improve the performance of your application, especially on mobile devices.

To use concurrent mode, you need to create a new React app using the create-react-app tool. Once you have created a new app, you can add the following code to your index.js file:

import React from 'react';
import ReactDOM from 'react-dom';

ReactDOM.createRoot(document.getElementById('root')).render(
  <React.StrictMode>
    <App />
  </React.StrictMode>
);

This code will enable concurrent mode for your app. You can now start writing code that can run in parallel.

Server components

Server components are a new type of React component that can be rendered on the server. This can improve the performance of your application by reducing the amount of data that needs to be sent to the client.

To use server components, you need to create a new React app using the create-react-app tool. Once you have created a new app, you can add the following code to your index.js file:

import React from 'react';
import ReactDOMServer from 'react-dom/server';

const App = () => {
  return (
    <div>
      Hello world!
    </div>
  );
};
const html = ReactDOMServer.renderToString(<App />);

This code will create a new React app that uses server components. You can now start writing code that can be rendered on the server.

Improvements to the React DevTools

The React DevTools are a set of tools that can be used to debug and profile React applications. In React 19, the DevTools have been updated with several new features, including:

• A new profiler that can be used to track the performance of your application
• A new component tree viewer that can be used to inspect the structure of your application
• A new event log that can be used to track the events that are fired by your application
• These new features make the React DevTools even more powerful and easier to use.

Conclusion

React 19 is a significant update to the React library. It includes several new features and improvements that make it even more powerful and easier to use. If you are using React, I encourage you to upgrade to React 19 today.