type
  jsobj {.importc.} = object
    update*: proc(){.nimcall.}
    call*: proc(s:d3_obj, x:int):int{.nimcall.}

  d3_obj {.importc.} = object
    linear* : proc(): jsobj{.nimcall.}

proc `()` (obj:jsobj; scale:float): float {.importc.}

var d3test {.importc,nodecl.}: d3_obj
var s = d3test.linear()
s.update()
echo "42=", s.call(d3test, 42)