function call another function in Module.Exports Node.JS

I'm trying to make a function call inside my module but I'm getting functionTwo is not define.

Module.js

// Module.exports
module.exports = function ( arg ) {

if(arg instanceof Object) {

    return functionTwo.apply(arg);
}

 functionOne: function(arg) {}

 functionTwo: function(arg) { //in here we may call functionOne or functionThree }

 functionThree: function() {}

Main.js

require(module)(typeObject);
require(module)(typeString);

So basically what I'm trying to do is if the type that is being passed from main.js to the module.js was an Object I want it to call a specific function and do something then just return, but I don't know maybe I'm defining the function wrong.