How to handle routes

When a request is made to the server, which matches a route definition, the associated callback functions kick in to process the request and send back a response. These callback functions are responsible for the dynamic behavior of the app; without them routes would simply be dumb interfaces that do nothing at all.

So far, we have been dealing with a single callback function for a route, but a route can have more than one callback function.

As mentioned earlier, the Express routing system is also built around the middleware concept—each route handler has the capability to send a response or pass on the request to the next route-handling middleware in the current or the next matching route.

All of a sudden route handling sounds a little more complicated than what we assumed earlier, doesn't it? Let's find out if it is so.

By now, we are all familiar with how a route definition looks like:

app.get('/', function(req, res) {
  res.send('welcome');
});

We have been using a single...