Playing with Javascript sub-classing and data hiding

sample.js

var Sample = (function (Sample) {

    "use strict";

    var SampleColumn = (function () {
            var SampleColumn = {};

            SampleColumn.parseColumns = function () {

                var columns = [],
                    column = {},
                    i;

                for (i = 0; i < Math.floor((Math.random() * 100) + 1); i += 1) {
                    column["COL" + i] = "VAL" + i;
                    columns.push(column);
                }

                return columns;
            };

            return SampleColumn;
        }()),

        SampleSheet = (function () {
            var SampleSheet = {};

            SampleSheet.create = function (sheetName) {
                var sheet = {};
                sheet[sheetName] = SampleColumn.parseColumns();
                return sheet;
            };

            return SampleSheet;
        }()),

        SampleWorkbook = (function () {

            var SampleWorkbook = {},

                sheetNames = [ 'First', 'Second', 'Third', 'Fourth', 'Fifth' ],
                sheets = [];

            SampleWorkbook.create = function (fileName) {
                var i;

                for (i = 0; i < sheetNames.length; i += 1) {
                    sheets.push(SampleSheet.create(sheetNames[i]));
                }

                return {
                    name: fileName,
                    sheets: sheets
                };

            };

            return SampleWorkbook;
        }());

    function createWorkbookFromFile(fileName) {
        return SampleWorkbook.create(fileName);
    }

    Sample.parseFile = function (f) {
        return createWorkbookFromFile(f);
    };

    return Sample;
}(Sample || {}));

var output = Sample.parseFile("fileName");
console.log(output);