var validateRequiredFields = (function () {

        var errorcount = 0;
        var formFieldData = []; // array will hold information about all required form fields

        var self = {

            prepareData: function (container) {

                var $selector = $(container),
                    $requiredFields = $selector.find('.js-required');

                return self.validateFields($requiredFields);

            },
            validateFields: function (fields) {

                errorcount = 0; // reset error counter before re-validating fields

                $.each(fields, function () {
                    var $this = $(this),
                        fieldName = $(this).attr('name'),
                        isFound = self.findInArr(fieldName, formFieldData);

                    if (isFound === -1) { // if this field is not found on form field array, push field information into array and add a listener which will listen for change event

                        var fieldObj = {};
                        fieldObj.name = $this.attr('name');
                        fieldObj.val  = $this.val();

                        formFieldData.push(fieldObj);

                        $this.on('change', function (e) {
                            e.preventDefault();
                            self.addOrRemoveInvalidClass($this);
                        });
                    }

                    self.addOrRemoveInvalidClass($this);
                });

                return (errorcount > 0) ? false : true;

            },
            addOrRemoveInvalidClass: function (field) {

                var $currentField = field;

                if (!$currentField.val()) {

                    errorcount.length ? errorcount-- : errorcount++;

                    if ($currentField.hasClass('select2-hidden-accessible')) { // to get correct input container from the Select2
                        $currentField = $currentField.parent().find('span.select2-selection');
                    }

                    $currentField.addClass('field-invalid');
                }
                else {

                    if ($currentField.hasClass('select2-hidden-accessible')) { // to get correct input container from the Select2
                        $currentField = $currentField.parent().find('span.select2-selection');
                    }

                    $currentField.removeClass('field-invalid');
                }
            },
            findInArr: function (value, array) {

                var isFound = -1;

                if (!array.length) {
                    return isFound;
                }

                for (var i = 0; i < array.length; i++) {
                    if (array[i].name === value) {
                        isFound = i;
                    }

                    if (i === array.length -1) {
                        return isFound;
                    }
                }
            }
        };

        return {
            validate: self.prepareData
        };

    })();