I don't know much about the tutorial web-server script.
When it comes to your situation, though, your best bet is to abstract away your data managing processes. In other words, you can make a set of services that take care of loading and saving your data. You could have methods like book.save()
or book.fetch()
.
Then in save()
and fetch()
you can return or insert an object literal or call for a JSON file.
Assuming that your product will be running on JSON data, you should be able to write another set of model services that call JSON data from the server rather any that you've hard written in the code or in a *.json file.