Separate files during a build


I am super super super new, and I’ve looked through this forum, and I can’t find anything like what I ask.

First, I tried starting a basic app from scratch with routes, but didn’t have any success. I may try gain later. But, in the meantime, I used the CLI to create an app, and when I build, all the html and javascript and such gets compiled into app.js. If this normal, and is there a way around this? I’d LIKE to be able to upload the web app to my host, and be able to tweak the end product a little here an there, in various html or css or js files as I feel the need. I’d prefer not to have to build the site every time I start playing around and experimenting with minor tweaks. Is it possible to build and all the js and css and html files remain as separate files?