So your JS code would, instead of hitting roblox directly, hit that proxy page on your own server.
That proxy page would go hit the main page(s) such as
and then it would either extract the data you need and send it back to your JS code in an easy to use format or it might just send the data unchanged.
This may not be a trivial task. Certainly if you know nothing about server-side coding it may be beyond you at this time.