How to Integrate react-native-web in an existing react native application

August 13, 2021

For using react native on web we can use the template of many build tools. I would like to use Create React App for this example.

Please make sure to execute all the commands mentioned below in the root directory.

Install required packages for web

yarn add react-native-web react-dom or npm install react-native-web react-dom

dev dependencies

yarn add --dev react-scripts babel-jest or npm install --save-dev react-scripts babel-jest

Create project structure

1. Create `public/` folder in root directory

mkdir public

Create a html file and add basic html

touch index.html

<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="utf-8" />
    <link href="%PUBLIC_URL%/favicon.ico" rel="icon" />
    <meta content="width=device-width, initial-scale=1" name="viewport" />
    <meta content="#ffffff" name="theme-color" />
    <meta content="React Native App" name="description" />
    <meta content="react native, react native web" name="keywords" />
    <link href="%PUBLIC_URL%/manifest.json" rel="manifest" />
 
    <title>React Native Web</title>
  </head>
  <body>
    <noscript>You need to enable JavaScript to run this app.</noscript>
    <div id="root"></div>
  </body>
</html>

Create manifest.json file to make it Progressive Web App

touch manifest.json

{
  "short_name": "React Native Web",
  "name": "React Native Web",
  "icons": [
    {
      "src": "favicon.ico",
      "sizes": "64x64 32x32 24x24 16x16",
      "type": "image/x-icon"
    }
  ],
  "start_url": ".",
  "display": "standalone",
  "theme_color": "#000000",
  "background_color": "#ffffff"
}

2. Create `src/` directory in root folder

Create serviceWorker.js for PWA

A progressive web application is a type of application software delivered through the web, built using common web technologies including HTML, CSS and JavaScript.

Download serviceWorker.js from the link serviceWorker.js

	// This optional code is used to register a service worker.
	// register() is not called by default.

	// This lets the app load faster on subsequent visits in production, and gives
	// it offline capabilities. However, it also means that developers (and users)
	// will only see deployed updates on subsequent visits to a page, after all the
	// existing tabs open on the page have been closed, since previously cached
	// resources are updated in the background.

	// To learn more about the benefits of this model and instructions on how to
	// opt-in, read https://bit.ly/CRA-PWA

	const isLocalhost = Boolean(
	window.location.hostname === 'localhost' \|\|
	// [::1] is the IPv6 localhost address.
	window.location.hostname === '[::1]' \|\|
	// 127.0.0.0/8 are considered localhost for IPv4.
	window.location.hostname.match(
	/^127(?:\.(?:25[0-5]\|2[0-4][0-9]\|[01]?[0-9][0-9]?)){3}$/,
	),
	);

	export function register(config) {
	if (process.env.NODE_ENV === 'production' && 'serviceWorker' in navigator) {
	// The URL constructor is available in all browsers that support SW.
	const publicUrl = new URL(process.env.PUBLIC_URL, window.location.href);
	if (publicUrl.origin !== window.location.origin) {
	// Our service worker won't work if PUBLIC_URL is on a different origin
	// from what our page is served on. This might happen if a CDN is used to
	// serve assets; see https://github.com/facebook/create-react-app/issues/2374
	return;
	}

	window.addEventListener('load', () => {
	const swUrl = `${process.env.PUBLIC_URL}/service-worker.js`;

	if (isLocalhost) {
	// This is running on localhost. Let's check if a service worker still exists or not.
	checkValidServiceWorker(swUrl, config);

	// Add some additional logging to localhost, pointing developers to the
	// service worker/PWA documentation.
	navigator.serviceWorker.ready.then(() => {
	console.log(
	'This web app is being served cache-first by a service ' +
	'worker. To learn more, visit https://bit.ly/CRA-PWA',
	);
	});
	} else {
	// Is not localhost. Just register service worker
	registerValidSW(swUrl, config);
	}
	});
	}
	}

	function registerValidSW(swUrl, config) {
	navigator.serviceWorker
	.register(swUrl)
	.then((registration) => {
	registration.onupdatefound = () => {
	const installingWorker = registration.installing;
	if (installingWorker == null) {
	return;
	}
	installingWorker.onstatechange = () => {
	if (installingWorker.state === 'installed') {
	if (navigator.serviceWorker.controller) {
	// At this point, the updated precached content has been fetched,
	// but the previous service worker will still serve the older
	// content until all client tabs are closed.
	console.log(
	'New content is available and will be used when all ' +
	'tabs for this page are closed. See https://bit.ly/CRA-PWA.',
	);

	// Execute callback
	if (config && config.onUpdate) {
	config.onUpdate(registration);
	}
	} else {
	// At this point, everything has been precached.
	// It's the perfect time to display a
	// "Content is cached for offline use." message.
	console.log('Content is cached for offline use.');

	// Execute callback
	if (config && config.onSuccess) {
	config.onSuccess(registration);
	}
	}
	}
	};
	};
	})
	.catch((error) => {
	console.error('Error during service worker registration:', error);
	});
	}

	function checkValidServiceWorker(swUrl, config) {
	// Check if the service worker can be found. If it can't reload the page.
	fetch(swUrl, {
	headers: {'Service-Worker': 'script'},
	})
	.then((response) => {
	// Ensure service worker exists, and that we really are getting a JS file.
	const contentType = response.headers.get('content-type');
	if (
	response.status === 404 \|\|
	(contentType != null && contentType.indexOf('javascript') === -1)
	) {
	// No service worker found. Probably a different app. Reload the page.
	navigator.serviceWorker.ready.then((registration) => {
	registration.unregister().then(() => {
	window.location.reload();
	});
	});
	} else {
	// Service worker found. Proceed as normal.
	registerValidSW(swUrl, config);
	}
	})
	.catch(() => {
	console.log(
	'No internet connection found. App is running in offline mode.',
	);
	});
	}

	export function unregister() {
	if ('serviceWorker' in navigator) {
	navigator.serviceWorker.ready
	.then((registration) => {
	registration.unregister();
	})
	.catch((error) => {
	console.error(error.message);
	});
	}
	}

view raw serviceWorker.js hosted with ❤ by GitHub

Create index.js file

import React from "react";
import { Text } from "react-native";
import ReactDOM from "react-dom";
import * as serviceWorker from "./serviceWorker";
 
const App = () => <Text>Hello</Text>;
 
ReactDOM.render(
  <React.StrictMode>
    <App />
  </React.StrictMode>,
  document.getElementById("root")
);
 
// If you want your app to work offline and load faster, you can change
// unregister() to register() below. Note this comes with some pitfalls.
// Learn more about service workers: https://bit.ly/CRA-PWA
serviceWorker.unregister();

Update script tag

Add "web": "react-scripts start" in package.json inside scripts tag

Execute npm run web or yarn web and it should start developer server at http://localhost:3000

References

https://necolas.github.io/react-native-web/docs/?path=/docs/guides-multi-platform--page
https://callstack.github.io/react-native-paper/using-on-the-web.html