I guess they mean something like this, which I find useful at quickly iterating over jq

  fzf --print-query --preview-window wrap --no-clear --preview 'cat file.json | jq {q}'

you can also pipe a curl in the above, but that will mean a lot of (slow) requests, so I have this snippet saved for running fzf --preview with jq on something from a web service

  curl -L https://datahub.io/core/covid-19/r/worldwide-aggregate.json > /tmp/foo && echo '' | fzf --print-query --preview-window wrap --no-clear --preview 'cat /tmp/foo | jq {q}'

now if you write something like

  .[0]["Confirmed"]

you will get a live preview of the result as you type

I did not know about `jiq`, so thanks for that tip, it looks like it does the same or something similar, but without the extra cruft of storing a temp file