The 'abeeway_battery_standalone.html' file includes all html and javascript code of the tool. Try it out (served from github) here.
Please note, that you can open the file in a web browser from a local file system even without using a web server.
The 'abeeway_battery.html' file uses the separate 'abeeway_battery.js' Node.js module. If you want to test the 'abeeway_battery.js' module, use the node test.js command.