Javascript JQuery Deferred promise ajax stuff

gistfile1.txt

    function bindBarCodeValidation() {
        $('#shoppingcart').debounced('input keyup', 'input[name="barcode"]', onSchedule, onFire, 500, rowIdentity);

        function onSchedule() {
            $(this).addClass('input-loader');
            return true;
        }

        function onFire() { validateBarcode($(this)); }

        function rowIdentity() { return $(this).closest('[data-row-id]').attr('data-row-id'); }

        function validateBarcode($target) {
            var barcodeInput = $target.val();
            if (_.isEmpty(barcodeInput.trim())) {
                onSuccess($target)();
                return;
            }
            ajaxGet('barcodes/' + barcodeInput).then(uniqueBarcodeInCart($target)).done(onSuccess($target)).fail(onError($target));
        }

        function uniqueBarcodeInCart($target) {
            return function() {
                var deferred = new $.Deferred();
                var barcode = $target.val();
                if (isUnique(barcode)) deferred.resolve();
                else deferred.reject();
                return deferred;
            };

            function isUnique(barcode) {
                var nonEmptyBarcodesInCheckout = _($('#shoppingcart').
                    find('input[name="barcode"]')).
                    map(function(elem) { return $(elem).val(); }).
                    filter(function(val) { return !_.isEmpty(val.trim()); }).
                    value();
                return _(nonEmptyBarcodesInCheckout).
                    filter(function(val) { return barcode.trim() === val.trim(); }).
                    value().length === 1;
            }
        }

        function onSuccess($target) {
            return function() {
                $target.removeClass('input-loader error');
                toggleSubmitEnablation();
            }
        }

        function onError($target) {
            return function() {
                $target.removeClass('input-loader'); $target.addClass('error');
                toggleSubmitEnablation();
            }
        }
    }

    function ajaxGet(suffix) {
        return $.ajax({
            url: "/yrityksille/mint/apiversion/1/" + suffix,
            contentType: 'application/json',
            type: 'GET'});
    }