Node.js "require" function and parameters

When I do:

lib = require('lib.js')(app)

is app actually geting passed in?

in lib.js:

exports = module.exports = function(app){}

Seems like no, since when I try to do more than just (app) and instead do:

lib = require('lib.js')(app, param2)

And:

exports = module.exports = function(app, param2){}

I don't get params2.

I've tried to debug by doing:

params = {}
params.app = app
params.param2 = "test"

lib = require("lib.js")(params)

but in lib.js when I try to JSON.stringify I get this error:

"DEBUG: TypeError: Converting circular structure to JSON"