How to Load Google API Javascript Library on Server?

[Roger Cauvin]

I'm trying to access the Google Sheets API from an hMailServer script. The script is Javascript and executes on a server, not in a browser. If you're unfamiliar with hMailServer, consider a script periodically running on a server as a chron job.

Google's documentation gives plenty of information on how to load the Google API Javascript client from HTML, but I haven't found any that describes how to do it from Javascript that runs on the server side and not in a browser context.

How do you load the Google API Javascript library in a script running on a server?

Also, what are the differences among:

https://apis.google.com/js/api.js
https://apis.google.com/js/client.js
https://apis.google.com/js/client:platform.js