jquery - 无法读取未定义的属性 'labels'

Question

我刚刚学习 Chart.js 的工作原理，因此我直接使用了 Chart.js API 页面上的示例代码，但它似乎不起作用。我将以下代码放入脚本标记中，并收到“无法读取未定义的属性‘标签’”错误。不确定这个错误意味着什么

$(function () {
                var ctx = $('#myCanv').get(0).getContext("2d");
                var myRadarChart = new Chart(ctx).Radar(data, options);
                var data = {
                    labels: ["Eating", "Drinking", "Sleeping", "Designing", "Coding", "Cycling", "Running"],
                    datasets: [
                        {
                            label: "My First dataset",
                            fillColor: "rgba(220,220,220,0.2)",
                            strokeColor: "rgba(220,220,220,1)",
                            pointColor: "rgba(220,220,220,1)",
                            pointStrokeColor: "#fff",
                            pointHighlightFill: "#fff",
                            pointHighlightStroke: "rgba(220,220,220,1)",
                            data: [65, 59, 90, 81, 56, 55, 40]
                        },
                        {
                            label: "My Second dataset",
                            fillColor: "rgba(151,187,205,0.2)",
                            strokeColor: "rgba(151,187,205,1)",
                            pointColor: "rgba(151,187,205,1)",
                            pointStrokeColor: "#fff",
                            pointHighlightFill: "#fff",
                            pointHighlightStroke: "rgba(151,187,205,1)",
                            data: [28, 48, 40, 19, 96, 27, 100]
                        }
                    ]
                };
                var options = {
                    //Boolean - Whether to show lines for each scale point
                    scaleShowLine: true,
                    //Boolean - Whether we show the angle lines out of the radar
                    angleShowLineOut: true,
                    //Boolean - Whether to show labels on the scale
                    scaleShowLabels: false,
                    // Boolean - Whether the scale should begin at zero
                    scaleBeginAtZero: true,
                    //String - Colour of the angle line
                    angleLineColor: "rgba(0,0,0,.1)",
                    //Number - Pixel width of the angle line
                    angleLineWidth: 1,
                    //String - Point label font declaration
                    pointLabelFontFamily: "'Arial'",
                    //String - Point label font weight
                    pointLabelFontStyle: "normal",
                    //Number - Point label font size in pixels
                    pointLabelFontSize: 10,
                    //String - Point label font colour
                    pointLabelFontColor: "#666",
                    //Boolean - Whether to show a dot for each point
                    pointDot: true,
                    //Number - Radius of each point dot in pixels
                    pointDotRadius: 3,
                    //Number - Pixel width of point dot stroke
                    pointDotStrokeWidth: 1,
                    //Number - amount extra to add to the radius to cater for hit detection outside the drawn point
                    pointHitDetectionRadius: 20,
                    //Boolean - Whether to show a stroke for datasets
                    datasetStroke: true,
                    //Number - Pixel width of dataset stroke
                    datasetStrokeWidth: 2,
                    //Boolean - Whether to fill the dataset with a colour
                    datasetFill: true,
                    //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].strokeColor%>\"></span><%if(datasets[i].label){%><%=datasets[i].label%><%}%></li><%}%></ul>"
                };
            });

Answer 1

我发现我的错误了! 在我声明任何数据或选项之前，雷达的创建位于代码的顶部。

var myRadarChart = new Chart(ctx).Radar(data, options);

此行必须放置在函数的底部

$(function () {
            var ctx = $('#myCanv').get(0).getContext("2d");
            var data = {
                labels: ["Eating", "Drinking", "Sleeping", "Designing", "Coding", "Cycling", "Running"],
                datasets: [
                    {
                        label: "My First dataset",
                        fillColor: "rgba(220,220,220,0.2)",
                        strokeColor: "rgba(220,220,220,1)",
                        pointColor: "rgba(220,220,220,1)",
                        pointStrokeColor: "#fff",
                        pointHighlightFill: "#fff",
                        pointHighlightStroke: "rgba(220,220,220,1)",
                        data: [65, 59, 90, 81, 56, 55, 40]
                    },
                    {
                        label: "My Second dataset",
                        fillColor: "rgba(151,187,205,0.2)",
                        strokeColor: "rgba(151,187,205,1)",
                        pointColor: "rgba(151,187,205,1)",
                        pointStrokeColor: "#fff",
                        pointHighlightFill: "#fff",
                        pointHighlightStroke: "rgba(151,187,205,1)",
                        data: [28, 48, 40, 19, 96, 27, 100]
                    }
                ]
            };
         var myRadarChart = new Chart(ctx).Radar(data, options);
        });