Why don’t javascript files work when deployed to web hosting?

I’m practicing downloading a production website, then uploading the website files to a web hosting service. But there is a problem with javascript files.

I used httrack to download the website, but unfortunately it doesn’t download some javascript files, no matter what configurations I’ve changed.
So, I downloaded the js files manually (through chrome network tab save as) and added the script tags manually to all html pages, and everything works like a charm. But, when I uploaded the website to 000webhost, javascript files DON’t WORK, although it’s been UPLOADED correctly.
My questions:
1 – Why js files not work? How to fix the problem? Or,
2 – How to let httrack download those js files correctly?
(the website is: www.classcentral.com)