catjson.sh

#!/bin/sh

jq -r '
    tostream
    | select(length > 1)
    | (
      .[0] | map(
        if type == "number"
        then "[" + tostring + "]"
        else "." + .
        end
      ) | join("")
    ) + " = " + (.[1] | @json)
  ' << INPUT
`cat $1`
INPUT