express-subdomain-handler takes the headache out of dynamic subdomain routing in Express. It captures the contents of any subdomain and writes them into the Express req.url. This means you can write specific route handlers for subdomain urls.

As you can see below, express-subdomain-handler can manage single or multiple subdomains.

• https://mysubdomain.example.com => '/subdomain/mysubdomain/'
• https://myexcellentsubdom.example.com/homepage => '/subdomain/myexcellentsubdom/homepage'
• https://first.second.example.com => '/subdomain/first/second/'
• https://first.second.example.com/another/page => '/subdomain/first/second/another/page'

npm install express-subdomain-handler

Add express-subdomain-handler to your express middleware stack (before your routes are specified). You need to specify what the base url of your site is ('example.com', 'example.local', etc), what you what subdomain urls to be prefixed with ('subdomain' by default) and whether you want logging turned on (false by default)

app.use( require('express-subdomain-handler')({ baseUrl: 'example.com', prefix: 'myprefix', logger: true }) );

Setup routes to catch subdomain urls so for https://mysubdomain.example.com/homepage I would write my route handler to look like this.

app.get('/myprefix/:thesubdomain/thepage', function(req, res, next){

  // for the example url this will print 'mysubdomain'
  res.send(req.params.thesubdomain);

});

If you like my stuff, follow me on Twitter