How can i request individual data to update a given .json file

i am trying to make a website where in the front page a svg is generated modelled after certain server sided hardware. I try to make this as modular as possible, since the hardware connected to the server can very a lot.

In short, i'm generating a svg with a .Json file that describes the hardware. But how can i add "software hooks" to the .json so that my frontpage knows it has to request the data value from the server.

Because i don't want to reload the .json with new values and have to regenerate the whole thing.