What are the drop-in dashboards for free data?

Question

JavaScript

I'm looking for a drop-in dashboard - just to throw spa .html and have it poll the url for json (or yaml).
Unstructured data KV - determine the type for displaying V by K (for example, K is ip_eth1_ip_address - it will show the "eth1 ip address" field with visualization through "ip" (well, for example, function show_ip...), etc.).
It's good if there is a fade-in \ fade-out to see the changed data.
The data is easy to create with a cron.
Is there such a thing in nature? A long time ago I saw something that turns the node on the server, but you can simply expand it through .sh.