app.mountpath

The app.mountpath property contains one or more path patterns on which a sub-app was mounted.

A sub-app is an instance of `express` that may be used for handling the request to a route.

const express = require('express');

const app = express(); // the main app
const admin = express(); // the sub app

admin.get('/', (req, res) => {
  console.log(admin.mountpath); // /admin
  res.send('Admin Homepage');
});

app.use('/admin', admin); // mount the sub app

It is similar to the baseUrl property of the req object, except req.baseUrl returns the matched URL path, instead of the matched patterns.

If a sub-app is mounted on multiple path patterns, app.mountpath returns the list of patterns it is mounted on, as shown in the following example.

const admin = express();

admin.get('/', (req, res) => {
  console.log(admin.mountpath); // [ '/adm{*splat}n', '/manager' ]
  res.send('Admin Homepage');
});

const secret = express();
secret.get('/', (req, res) => {
  console.log(secret.mountpath); // /secr{*splat}t
  res.send('Admin Secret');
});

admin.use('/secr{*splat}t', secret); // load the 'secret' router on '/secr{*splat}t', on the 'admin' sub app
app.use(['/adm{*splat}n', '/manager'], admin); // load the 'admin' router on '/adm{*splat}n' and '/manager', on the parent app