In this chapter, we have started building out our own application by creating new middleware and service modules. We've read user-submitted data from forms and acted on it. We've implemented a JSON API on the server side and communicated with this from the client using Ajax. We've used partial views to render common components.

So far, we've seen how to write JavaScript code and implement various functionality in Node.js. This is good for prototyping, but isn't enough for a maintainable project. It's also important to write automated tests for our code, which is the subject of the next chapter.