We're going to add a lot of new functionality to the application, and it won't be possible to explain every piece of code before we encounter it. Several of the new functions depend on at least one other function, which means that you will see some of the functions for the first time while a different function is being introduced.

It's important, therefore, that you concentrate on whichever function is being explained and wait until later in the chapter to understand the whole piece of code. New functions that are explained later in the chapter will be noted as we progress. In order to help you understand what the code does as you go along, it is worth quickly reviewing the actual functionality of the application now. You can find a link to a hosted version of the application within the GitHub page referenced in the introduction to this chapter. It is definitely worth visiting this page to see the application in action yourself.

In terms of the functionality...