I am moving selected item from a list to another.

i want to increase the quantity of a field it the item already exists. Please see my existing code is below

  <script src="//code.jquery.com/jquery-1.11.3.min.js" type="text/javascript"></script>
<script type="text/javascript">
    //var dfd = $.Deferred();
    function AddToCart() {
        var context = SP.ClientContext.get_current();
        //var siteUrl = 'https://xxx.sharepoint.com/sites/Developer';
        //you don't use clientContext
        //var clientContext = new SP.ClientContext(siteUrl);
        var web = context.get_web();
        context.load(web);
        alert('1');
        var sourceId = SP.ListOperation.Selection.getSelectedList();
        var source = web.get_lists().getById(sourceId);

        var dfd = $.Deferred();
        alert('debut');
        var oList = context.get_web().get_lists().getByTitle('Chart');
        context.load(oList);

        var selectedItems = SP.ListOperation.Selection.getSelectedItems(context);
        var spItems = [];

          alert('debut');
        for (i = 0; i < selectedItems.length; i++) {
            var currentItem = source.getItemById(selectedItems[i].id);
            //alert(selectedItems[i].id);
            context.load(currentItem);
            spItems.push(currentItem);

        }
        context.executeQueryAsync(Function.createDelegate(this, function (sender, args) {

            for (var j = 0; j < spItems.length; j++) {
                //alert(pItems[j].get_item('Title'));
                var Match = Compare(spItems[j].get_item('Product_x0020_Name'));
                alert(Match + "Match variable");
                if (Match == 1) {
                    alert("Item already exists in the chart");
                    oListItem.set_item('QTY', spItems[j].get_item('QTY') + 1);
                    oListItem.update();
                }
                else if (Match == 0) {
                    alert("Item not in the chart");
                    var itemCreateInfo = new SP.ListItemCreationInformation();
                    var oListItem = oList.addItem(itemCreateInfo);
                    oListItem.set_item('Title', spItems[j].get_item('Title'));
                    //alert(spItems[j].get_item('Title'));
                    oListItem.set_item('Item', spItems[j].get_item('Item'));
                    oListItem.set_item('Product_x0020_Name', spItems[j].get_item('Product_x0020_Name'));
                    oListItem.set_item('Description', spItems[j].get_item('Description'));
                    oListItem.set_item('Price', spItems[j].get_item('Price'));
                    oListItem.set_item('Department', spItems[j].get_item('Department'));
                    oListItem.set_item('Branch', spItems[j].get_item('Branch'));
                    oListItem.update();
                }

                // oListItem.set_item('QTY', spItems[j].get_item('QTY') + 1);


                //alert(spItems[j].get_item('Product_x0020_Name'));
                //oList.update();                
            }
            context.executeQueryAsync(success);
            //   alert('done');

        }), Function.createDelegate(this, error));


        function success(sender, args) {
            alert('Added to chart!');
            // window.location.reload(true);
            window.location.href = window.location.href;
        }

        function error(sender, args) { alert('error'); }
    }

    function Compare(str) {
        alert('Compare : ' + str);
        var clientContext = SP.ClientContext.get_current();
        list = clientContext.get_web().get_lists().getByTitle('Chart');
        var skillcamlQuery = new SP.CamlQuery();

        skillcamlQuery.set_viewXml("<View><Query><Where><Eq><FieldRef Name='Product_x0020_Name' /><Value Type='Text'>" + str + "</Value></Eq></Where></Query></View>");
        this.skillcollListItem = list.getItems(skillcamlQuery);

        clientContext.load(skillcollListItem);

        var callback = clientContext.executeQueryAsync(Function.createDelegate(this, function () { _returnParam = onValidateClientSucceeded(); }), Function.createDelegate(this, function () { _returnParam = onValidateClientFailed(); }));

       // alert('compare 1');

        function onValidateClientSucceeded(sender, args) {
           dfd.resolve(sender, args);


            alert("Compare successful");
            if (skillcollListItem.get_count() >= 1) {

                alert('match found');
                return 1
            }
            else {
                alert('mach not found');
                return 0
            }
        }
        function onValidateClientFailed(sender, args) {
            dfd.resolve(sender, args);

        }
    }
    </script>
    <input name="btnApprove" onclick="AddToCart()" type="button" value="Add To Cart" />