Route parameters are named URL segments that are used to capture the values specified at their position in the URL. The captured values are populated in the req.params object, with the name of the route parameter specified in the path as their respective keys.

Route path: /users/:userId/books/:bookId

Request URL: http://localhost:3000/users/34/books/8989

req.params: { “userId”: “34”, “bookId”: “8989” }

To define routes with route parameters, simply specify the route parameters in the path of the route as shown below.

app.get('/users/:userId/books/:bookId', (req, res) => {

  res.send(req.params)

})