req.baseUrl

The URL path on which a router instance was mounted.

The req.baseUrl property is similar to the mountpath property of the app object, except app.mountpath returns the matched path pattern(s).

For example:

var greet = express.Router();

greet.get('/jp', function (req, res) {
  console.log(req.baseUrl); // /greet
  res.send('Konnichiwa!');
});

app.use('/greet', greet); // load the router on '/greet'

Even if you use a path pattern or a set of path patterns to load the router, the baseUrl property returns the matched string, not the pattern(s). In the following example, the greet router is loaded on two path patterns.

app.use(['/gre+t', '/hel{2}o'], greet); // load the router on '/gre+t' and '/hel{2}o'

When a request is made to /greet/jp, req.baseUrl is “/greet”. When a request is made to /hello/jp, req.baseUrl is “/hello”.