Figured it out.
I’m sure I probably got it backwards, but what worked was saving multiple copies of the slider.js file and relabeling the ID selector.
I think I would have rather had done it the way AlenAbdula had suggested, which also seems “cleaner”, doing it all in the same .js file, but when I tried doing it that way, it did not function for me. I’m sure my structure or syntax may have been wrong, perhaps the way I put it together, but at least now I’ve got it working.
Thank you everyone for your suggestions and help !