How to split single page static html?

Question

Node.js

Good afternoon, I am writing a site for embedded systems, all in one Html css and JS, but over time I have produced so much that it is already difficult to parse something, so I decided to figure out the assembly. Initially, I installed webpack and divided all js into smaller parts, but somehow everything is laborious there, figure out how to set it up, and everything changes quickly, I don’t have time to follow because, not quite my profile, so I decided to switch to node, do minimal build setup from several html one, and also JS + minification. The whole question is how to do this on node, I found a lot of examples, but all with app.get("/contact"....., and I don’t have requests for a real page, I did it on JS on the event of hiding the opening of the necessary divs.
Well, I would also like to do something like a function on Html to wrap the button in it and stuff it on several pages with calling different events on click, on what can this be done? I dug aside before Html processors
until I could choose which one to do everything on, the syntax is somehow very different.