Import an other JS file in modules directory.

The way we usually do it in modules is:

// your other stuff

exports.connect = function (p1,p2,p3,p4) {
  return new stepperClass(p1,p2,p3,p4);
}

then:

var stepper = require("stepper").connect(...);

There's a template on the website here that you might find handy.