problem with babel compilation of recursion

gistfile1.js

var invariant = require('invariant');
var path = require('path');
var helpers = require('./DSLHelpers');

module.exports = (function () {
    function RegistryDSL() {
        _classCallCheck(this, RegistryDSL);
        this.dependencyDeclarations = [];

...
    }

    _createClass(RegistryDSL, [{
        key: 'requireDirectoryRecursively',
        value: function requireDirectoryRecursively(dir) {
            var _this2 = this;

            invariant(dir, 'You must provide a valid directory');
            var absoluteDir = path.join(appRoot.path, dir);
            
            var result = helpers.recurseDirectories(absoluteDir);

            console.log(result);  // --> returns empty array []

            result.forEach(function (x) {
                return _this2.dependencyDeclarations.push(x);
            });
            return this;
        }
    }]);

    return RegistryDSL;
})();

=============

var Dependency = require('./Dependency');
var fs = require('fs');
var appRoot = require('./appRoot');

module.exports = {
    recurseDirectories: function recurseDirectories(dir) {
        var _this = this;

        var result = fs.readdirSync(dir).map(function (x) {
            var stat = fs.statSync(dir + '/' + x);
            if (stat && stat.isDirectory()) {
                _this.recurseDirectories(dir + '/' + x);
            }
            return x;
        }).filter(function (x) {
            return x.endsWith('.js');
        }).map(function (x) {
            return _this.processFile(x, dir);
        });

        console.log(result);  // --> returns array full of objects;

        return result;
    },

    processFile: function processFile(file, dir, groupName) {
        if (!file.endsWith('.js')) {
            return;
        }
        file = file.replace('.js', '');
        var path = dir.replace(appRoot.path, '') + '/' + file;
        return new Dependency({ name: file, path: path, internal: true, groupName: groupName || '' });
    }

};