This is an experimental project integrating ReactJS with unity UIElements.

Add a dependency into your manifest.json.

{
  "dependencies": {
    "com.mkmarek.uielements.react": "https://github.com/mkmarek/unity-react-uielements.git#releases/vX.X.X",
  }
}

For released version numbers check the releases tab.

1. In your unity Assets folder create a Resources folder.
2. Using whatever file editor you like create a index.jsx file inside that Resources folder.
3. Paste the following content inside the index.jsx file.

import React from 'react';
import { render } from 'unity-renderer';

const style = {
  width: "80%",
  height: "80%",
  backgroundColor: "#ffffff",
  fontSize: 21,
  alignSelf: 'Center',
  alignItems: 'Center',
  justifyContent: 'Center'
}

function App() {
  return <visualElement style={style}>
    Hello Unity!
  </visualElement>
}

render(<App />)

4. In your Unity scene create a new empty object and add PanelRenderer and EventSystem monobehaviours to it as you would normaly do for runtime UIElements.
5. Attach ReactRuntime monobehaviour to the object and drag your index.jsx into the Root field.

Set the root property to your index.jsx. Just drag it from your Resources folder into the field.

For bigger example look into the examples folder.

Check the wiki for more information.