下面的代码使用AJAXJSON从mysql中提取数据，并绘制动态图表，效果很好，但当我的问题是更新图表时。

当我尝试更新图表时，我遇到以下错误：

未捕获引用错误：未定义g

这已经定义好了

所有这些代码都在文档中

//从服务器获取数据

  $.ajax({
        type: 'POST',
        url: 'php/proccess.php',
        data: {
            type: "jobgraph",
            job: job
        },
        dataType: "json",
        success: function(response) {
            //console.log(response);
            var i = 0;
            $.each(response, function(key, value) {

                test[i] = [new Date(value[0]), value[1] / 1000, value[2]];
                i++;
            });


            if (test) {
                document.addEventListener("mousewheel", function() {
                    lastClickedGraph = null;
                }, false);
                document.addEventListener("click", function() {
                    lastClickedGraph = null;
                }, false);


                if (response) {
                    var g = new Dygraph(document.getElementById("noroll"),

                        test, {
                            labels: ["Date", "Voltage", "Temp"],
                            digitsAfterDecimal: 3,

                            interactionModel: {
                                'mousedown': downV3,
                                'mousemove': moveV3,
                                'mouseup': upV3,
                                'click': clickV3,
                                'dblclick': referesh,
                                'mousewheel': scrollV3
                            }

                        }
                    );

                }

            }


        },
        error: function(jqXHR, textStatus, errorThrown) {
            if (jqXHR.status == 500) {
                alert('Internal error: ' + jqXHR.responseText);
            } else {
                console.log(errorThrown);
            }
        },


    });

   // update Data every 2 second by pulling new data from mysql server   

  window.intervalId = setInterval(function() {