// foo.js
var calc = require('./calc.js');

var a = 3, b = 5;
console.log(calc.calc(a, b));

// math.js
module.exports {
    calc: function(a, b) {
        // I need to call another function which does the math right here.
    }
}

// math.js
module.exports {
    calc: function(a, b) {
        function b(a, b) {
            return a+b;
        }
    }
}