Each Express application is a middleware on its own, so it can be mounted into another application. This feature makes it easy to plug subapplications into a parent one. Possible use cases include the following points:
Creating applications in a modular way, where each subapplication is totally independent of the others and possibly developed by other team members
Adding a blogging platform or a forum to an endpoint
Integrating third-party tools such as a monitoring dashboard or an FTP client along with a text editor
There are two possible approaches we can take when working with mountable applications: either the main application deals with crosscutting concerns such as logging and error handling, or the subapplications handle these things on their own. If we require third-party applications, we might not be able to control some of these aspects, but if we are creating a modular web application from scratch, then it's our choice to begin with.
Next, we will create an...