Serving multiple react apps with client-side routing in Express

After some tinkering I was able to achieve this without using virtual hosts. I used the first idea you gave in the question, except I left the main app at the root (i.e. /).

// when going to `/app2`, serve the files at app2/build/* as static files
app.use('/app2', express.static(path.join(__dirname, 'app2/build')))
// when going to `/`, serve the files at mainApp/build/* as static files
app.use(express.static(path.join(__dirname, 'mainApp/build')))


// These are necessary for routing within react
app.get('app2/*', (req, res) => {
  res.sendFile(path.join(__dirname + '/app2/build/index.html'))
})

app.get('*', (req, res) => {
  res.sendFile(path.join(__dirname + '/mainApp/build/index.html'));
});

After this, I went into mainApp/package.json and added

"proxy": "http://localhost:4141"

:4141 is the port that the express server is running on. This line will make calls to fetch('/some/route') go back to the server instead of into your react app itself.

Finally, we go to app2/package.json and add

"proxy": "http://localhost:4141/app2",
"homepage": "/app2"

I believe that the key here is the "homepage" key. The way I understand it, when react starts it searches for some static files at its homepage, and without the "homepage" piece I was only able to get either a blank white screen or the mainApp.

I hope this helps someone out there!

---

EDIT

I have since changed from serving my create-react-apps through my express server to serving them through netlify. Now I don't need to worry about this express setup, or the homepage key in package.json. The express server lives by itself, and the react apps can still both use the same api, and deployment is much easier. Setup with netlify is trivial.

After struggling for a while with this problem I've found a possible solution without compromising the original setup.

We used Express vhost package to setup handling of requests through virtual domains.

When you create your app instance, you should initialize as many apps with express as you want to expose separately (in our case its three separate apps plus the original app instance)

// Create an express instance
const app = express();
const appAdmin = express();
const appClient = express();
const appVendor = express();

After that you need to install vhost and import it. Then with specifying the static folder for each app you can handle serving the static files separately, while the remaining part deals with handling the request for the given subdomains respectively.

  appAdmin.use(express.static(path.join(__dirname, 'build-admin')));
  appClient.use(express.static(path.join(__dirname, 'build-client')));
  appVendor.use(express.static(path.join(__dirname, 'build-vendor')));

  appAdmin.use((req, res, next) => {
    return res.sendFile(path.resolve( __dirname, 'build-admin' , 'index.html'));
  });

  appClient.use((req, res, next) => {
    return res.sendFile(path.resolve( __dirname, 'build-client' , 'index.html'));
  });

  appVendor.use((req, res, next) => {
    return res.sendFile(path.resolve( __dirname, 'build-vendor' , 'index.html'));
  });

  app.use(vhost('domain.com', appClient));
  app.use(vhost('www.domain.com', appClient));
  app.use(vhost('a.domain.com', appAdmin));
  app.use(vhost('b.domain.com', appVendor));

Don't forget to add the desired subdomains in your domain's DNS registry. Example:

...records
CNAME   vendor  @
CNAME   admin   @