图表Js无法读取未定义的属性"长度"

Question

使用Chart js我试图将数据从Ajax调用提供给Chart.我发现了一些其他帖子,人们建议延迟画布加载,但似乎没有任何效果.目前这是我下面的内容,我得到的错误是

$(function () {

GetChartData();

    function GetChartData() {
    $.ajax({
        url: ajaxURL,
        method: 'GET',
        dataType: 'json',
        success: function (d) {
            //-------------
            //- BAR CHART -
            //-------------
            var barChartData = d;
            var barChartCanvas = $("#barChart").get(0).getContext("2d");
            var barChart = new Chart(barChartCanvas);
            // console.log(datajson);
            //barChartData.datasets[1].fillColor = "#00a65a";
            //barChartData.datasets[1].strokeColor = "#00a65a";
            //barChartData.datasets[1].pointColor = "#00a65a";
            var barChartOptions = {
                //Boolean - Whether the scale should start at zero, or an order of magnitude down from the lowest value
                //scaleBeginAtZero: true,
                //Boolean - Whether grid lines are shown across the chart
                scaleShowGridLines: true,
                //String - Colour of the grid lines
                scaleGridLineColor: "rgba(0,0,0,.05)",
                //Number - Width of the grid lines
                scaleGridLineWidth: 1,
                //Boolean - Whether to show horizontal lines (except X axis)
                scaleShowHorizontalLines: true,
                //Boolean - Whether to show vertical lines (except Y axis)
                scaleShowVerticalLines: true,
                //Boolean - If there is a stroke on each bar
                barShowStroke: true,
                //Number - Pixel width of the bar stroke
                barStrokeWidth: 2,
                //Number - Spacing between each of the X value sets
                barValueSpacing: 5,
                //Number - Spacing between data sets within X values
                barDatasetSpacing: 1,
                multiTooltipTemplate: "<%=datasetLabel%>: <%= value + ' %' %>",
                //String - A legend template
                legendTemplate: "<ul class=\"<%=name.toLowerCase()%>-legend\"><% for (var i=0; i<datasets.length; i++){%><li><span style=\"background-color:<%=datasets[i].fillColor%>\"></span><%if(datasets[i].label){%><%=datasets[i].label%><%}%></li><%}%></ul>",
                //Boolean - whether to make the chart responsive
                responsive: true,
                maintainAspectRatio: true
            };


            barChartOptions.datasetFill = false;
            barChart.Bar(barChartData, barChartOptions);


        }
    });
    }
});

在这里更新显示非AJAX如何工作

下面的代码将获取Ajax get请求的结果(我将其从转储到控制台获得)并创建同一事物的"硬编码"版本.技术上唯一不同的是,在页面时加载数据,第二次在数据加载后非常短暂.

 var chartData = {
    "labels": [
      "April"
    ],
    "datasets": [
      {
          "label": "Not Sure What to Put Here",
          "fillColor": "#662B60",
          "strokeColor": "#662B60",
          "pointColor": "#662B60",
          "pointStrokeColor": "#662B60",
          "pointHighlightFill": "#662B60",
          "pointHighlightStroke": "#662B60",
          "data": [
            1
          ]
      },
      {
          "label": "Not Sure What to Put Here",
          "fillColor": "#88B56E",
          "strokeColor": "#88B56E",
          "pointColor": "#88B56E",
          "pointStrokeColor": "#88B56E",
          "pointHighlightFill": "#88B56E",
          "pointHighlightStroke": "#88B56E",
          "data": [
            1
          ]
      },
      {
          "label": "Not Sure What to Put Here",
          "fillColor": "#48CA2B",
          "strokeColor": "#48CA2B",
          "pointColor": "#48CA2B",
          "pointStrokeColor": "#48CA2B",
          "pointHighlightFill": "#48CA2B",
          "pointHighlightStroke": "#48CA2B",
          "data": [
            0.83
          ]
      }
    ]
};


    //-------------
    //- BAR CHART -
    //-------------
var barChartData = chartData;
    var barChartCanvas = $("#barChart").get(0).getContext("2d");
    var barChart = new Chart(barChartCanvas);

    //barChartData.datasets[1].fillColor = "#00a65a";
    //barChartData.datasets[1].strokeColor = "#00a65a";
    //barChartData.datasets[1].pointColor = "#00a65a";
    var barChartOptions = {
        //Boolean - Whether the scale should start at zero, or an order of magnitude down from the lowest value
        //scaleBeginAtZero: true,
        //Boolean - Whether grid lines are shown across the chart
        scaleShowGridLines: true,
        //String - Colour of the grid lines
        scaleGridLineColor: "rgba(0,0,0,.05)",
        //Number - Width of the grid lines
        scaleGridLineWidth: 1,
        //Boolean - Whether to show horizontal lines (except X axis)
        scaleShowHorizontalLines: true,
        //Boolean - Whether to show vertical lines (except Y axis)
        scaleShowVerticalLines: true,
        //Boolean - If there is a stroke on each bar
        barShowStroke: true,
        //Number - Pixel width of the bar stroke
        barStrokeWidth: 2,
        //Number - Spacing between each of the X value sets
        barValueSpacing: 5,
        //Number - Spacing between data sets within X values
        barDatasetSpacing: 1,
        multiTooltipTemplate: "<%=datasetLabel%>: <%= value + ' %' %>",
        //String - A legend template
        legendTemplate: "<ul class=\"<%=name.toLowerCase()%>-legend\"><% for (var i=0; i<datasets.length; i++){%><li><span style=\"background-color:<%=datasets[i].fillColor%>\"></span><%if(datasets[i].label){%><%=datasets[i].label%><%}%></li><%}%></ul>",
        //Boolean - whether to make the chart responsive
        responsive: true,
        maintainAspectRatio: true
    };


    barChartOptions.datasetFill = false;
    barChart.Bar(barChartData, barChartOptions);

更新 我从chart.js的最小版本更改为完整版本,因此我可以看到它出错的确切位置.

这是来自chrome控制台的图像

Answer 1

问题是,当您的代码执行时,尚未创建画布.您应该将代码包装在函数中,并将该函数分配给window.onload事件.您可以在下面看到示例代码.

window.onload = function() {
  var ctx = document.getElementById("myChart");
  var lineChart = new Chart(ctx, {
    type: 'line',
    data: {
      labels: ["Jan", "Feb", "Mar", "Apr", "May", "Jun", "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"],
      datasets: [{
        label: "2015",
        data: [10, 8, 6, 5, 12, 8, 16, 17, 6, 7, 6, 10]
      }]
    }
  })
}

<html>

<head>
  <script src="https://cdnjs.cloudflare.com/ajax/libs/Chart.js/2.5.0/Chart.js"></script>

</head>

<body>
  <canvas id="myChart"></canvas>
</body>

</html>

Answer 2

找到答案,

必须首先解析Ajax结果.

结果修复

var barChartData = JSON.parse(d);