Access object context from prototype functions JavaScript

I am not professional developer, I have problems with object scope.

Here is my class code

// Table list module
        function DynamicItemList(data, settings, fields) {
            if (!(this instanceof DynamicItemList)) {
                return new DynamicItemList(data, settings, fields);
            }
            this.data = data;
            this.settings = settings;
            this.fields = fields;
            this.dataSet = {
                "Result": "OK",
                "Records": this.data ? JSON.parse(this.data) : []
            };
            this.items = this.dataSet["Records"];
            this.generateId = makeIdCounter(findMaxInArray(this.dataSet["Records"], "id") + 1);
            this.dataHiddenInput = $(this.settings["hidden-input"]);
        }

        DynamicItemList.RESULT_OK = {"Result": "OK"};
        DynamicItemList.RESULT_ERROR = {"Result": "Error", "Message": "Error occurred"};
        DynamicItemList.prototype = (function () {
            var _self = this;
            var fetchItemsList = function (postData, jtParams) {
                return _self.dataSet;
            };
            var createItem = function (item) {
                item = parseQueryString(item);
                item.id = this.generateId();
                _self.items.push(item);
                return {
                    "Result": "OK",
                    "Record": item
                }
            };
            var removeItem = function (postData) {
                _self.items = removeFromArrayByPropertyValue(_self.items, "id", postData.id);
                _self.dataSet["Records"] = _self.items;
                _self.generateId = makeIdCounter(findMaxInArray(_self.dataSet["Records"], "id") + 1);
                return DynamicItemList.RESULT_OK;
            };
            return {
                setupTable: function () {
                    $(_self.settings["table-container"]).jtable({
                        title: _self.settings['title'],
                        actions: {
                            listAction: fetchItemsList,
                            deleteAction: removeItem
                        },
                        fields: _self.fields
                    });
                },
                load: function () {
                    $(_self.settings['table-container']).jtable('load');
                },
                submit: function () {
                    _self.dataHiddenInput.val(JSON.stringify(_self.dataSet["Records"]));
                }
            };
        })();

I have problems with accessing object fields.

I tried to use self to maintain calling scope. But because it is initialized firstly from global scope, I get Window object saved in _self.

Without _self just with this it also doesn't work . Because as I can guess my functions fetchItemsList are called from the jTable context and than this points to Window object, so I get error undefined.

I have tried different ways, but none of them work.

Please suggest how can I solve this problem.

Thx.