How to change value of devExtreme editing popup items?

Question

  editing: {
        mode: "popup",
        allowUpdating: true,
        allowAdding: true,
        allowDeleting: true,
        popup: {
            title: "test",
            showTitle: true,
            width: 1200,
            height: 200,
            position: {
                my: "center",
                at: "center",
                of: window
            },
        },
        form: {
            labelLocation: "left",
            colCount: 9,
            items: [{
                colSpan:2,
                itemType: "group",
                caption: " ",
                items: [
                    {
                        dataField: "Prefix",
                    },
                    
                ]
            },{
                colSpan:2,
                itemType: "group",
                caption: " ",
                items: [
                    {
                        dataField: "Position",
                        editorOptions: {
                           onValueChanged: function(e) {
console.log($("#gridContainer").dxDataGrid('instance').option('editing').form.items[0].items[0].value);
                           }
                        },
                    },
                    
                ]
            }]}
        }

How can I change value in devExtreme -> dxDataGrid -> editing -> popup -> column? When I 'click edit in datagrid and change the value of another column when I change the value of any column' is what I have to do. I'm try to access another columns to

console.log($("#gridContainer").dxDataGrid('instance').option('editing').form.items[0].items[0].value,

but not working When I try $('[id$="Prefix"]').val("123") , text changes but value is not passed at insert How can I change other or certain column value / text change?

The devExtreme version was 19.2 / IDE was IntelliJ / Jquery version was 3.2.1 Please help me..