Question

TypeError 未正确读取属性

2014-08-26

7446

javascript arrays typeerror chart.js

我遵循 Chartjs 文档，并且我的数据对象中有两个数组（标签和数据集），当我尝试在数据集数组中定义属性时，似乎遇到了错误消息 Uncaught TypeError: Cannot read property 'datasets' of undefined ，并且无法找出原因。信息与文档准确匹配，但由于某种原因，它不起作用。

HTML：

<!doctype html>
<html>

    <head>
        <title>Google Super Proxy Test</title>
        <script src="Chart.min.js"></script>
        <script src="chart-options.js"></script>
    </head>

<body>

    <div style="width: 50%">
        <canvas id="sessions-graph" height="450" width="600"></canvas>
    </div>


</body>

</html>

charts-options.js

window.onload = function(){

    // Get the context of the canvas element
    var ctx = document.getElementById("sessions-graph").getContext("2d");
    var sessionsGraph = new Chart(ctx).Bar(data); //Create a chart with "data" array

    var data = {
        labels: ["January", "February", "March", "April", "May", "June", "July"],
        datasets: [
            {
                label: "My First dataset",
                fillColor: "rgba(220,220,220,0.5)",
                strokeColor: "rgba(220,220,220,0.8)",
                highlightFill: "rgba(220,220,220,0.75)",
                highlightStroke: "rgba(220,220,220,1)",
                data: [65, 59, 80, 81, 56, 55, 40]
            }
        ]
    };


    Chart.defaults.global = {

        //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 - 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

    }

}

Answer 1

您必须在将 data 传递给函数之前对其进行分配：

var data = {
    labels: ["January", "February", "March", "April", "May", "June", "July"],
    datasets: [
        {
            label: "My First dataset",
            fillColor: "rgba(220,220,220,0.5)",
            strokeColor: "rgba(220,220,220,0.8)",
            highlightFill: "rgba(220,220,220,0.75)",
            highlightStroke: "rgba(220,220,220,1)",
            data: [65, 59, 80, 81, 56, 55, 40]
        }
    ]
};

var sessionsGraph = new Chart(ctx).Bar(data); //Create a chart with "data" array

您可能还应该在调用 Chart.default.global 之前对其进行分配，但我不确定何时使用它。