Could JS use the node-ffi to process the variable parameter function of dll written with C/C++?

In a general way we could write as

var libfunc = ffi.Library('./func',{
  'func': ['void',['int', 'int']]
})

with function void func(int x, int y). The dynamic link library with C/C++ exports the variable parameter function, such as: void func(int x, int y, ...). How can I declare this in js with node-ffi ?