AjaxDataSource: how to reuse JSON data from JavaScript?

I already posted on stackoverflow this question (it is far more readable than groups) and there is some code to help to describe what I mean:
  https ://stackoverflow.com/questions/45939886/bokeh-ajaxdatasource-how-to-reuse-json-data-in-javascript)

I use AjaxDataSource. I would like to use the JSON data passed to the plot for further elaboration in JS: in my case I want to set a gauge to the last JSON value, but it could also be useful to print the current value as text.

Is there any possibility to reuse the data?
PS: my knowledge of JS is null, so I would need some extra help with the syntax :frowning: