无法读取值为0或null的未定义ChartistJs的属性'_index'

Question

我将chartistJS用于网页上的图表。我已经从图表专家提供的选项中了解了“ onClick”功能。

请在下面找到我的代码：

 public horizontalBarchartoptions = {
      'onClick' : function (evt, item) {
        var index = item[0]['_index']
        var reportId = latestScanReportID[index];
        routingFunct.navigate(["./resultPage/"+reportId]);
      },
      tooltips: {
              callbacks: {
                  label: function(tooltipItem) {
                      return  " "+ Number(tooltipItem.xLabel)+" issue(s)";
                  }
              }
          },
          scales: {
            yAxes: [{
              scaleLabel: {
                display: true,
                labelString: 'Volume'
              }, 
              display: true,
              labelString: 'Density',
              ticks: {
                  mirror: true,
                  autoSkip: false,
                  padding: -30,
                  fontColor: '#fff'
                }}],
            xAxes: [{
              scaleLabel: {
                display: true,
                labelString: '# Issues'
              }, 
              ticks: {
                min: 0,
                userCallback: function(label, index, labels) {
                  // when the floored value is the same as the value we have a whole number
                  if (Math.ceil(label) === label) {
                      return label;
                  }
                }                
            },
            }]
         }       
        };

单击条形时，以上代码将重定向到该特定条形ID的结果页面以下是相同图片：In this image when clicked on scan 1 - scan 4 it is redirected to results page当单击扫描5时，由于扫描5的值为0

，它将引发以下异常。

ERROR TypeError: Cannot read property '_index' of undefined

我可以从-1开始标注轴标签，但这不是首选的解决方案，请您提出另一种解决此问题的方法。

提前感谢

Answer 1

我建议至少在'item'没有元素时进行处理：

 public horizontalBarchartoptions = {
      'onClick' : function (evt, item) {
        if (item != null && item != undefined) {
           if (item.length > 0) {
              var index = item[0]['_index']
              var reportId = latestScanReportID[index];
              routingFunct.navigate(["./resultPage/"+reportId]);
           }
        }
      },
      tooltips: {
              callbacks: {
                  label: function(tooltipItem) {
                      return  " "+ Number(tooltipItem.xLabel)+" issue(s)";
                  }
              }
          },
          scales: {
            yAxes: [{
              scaleLabel: {
                display: true,
                labelString: 'Volume'
              }, 
              display: true,
              labelString: 'Density',
              ticks: {
                  mirror: true,
                  autoSkip: false,
                  padding: -30,
                  fontColor: '#fff'
                }}],
            xAxes: [{
              scaleLabel: {
                display: true,
                labelString: '# Issues'
              }, 
              ticks: {
                min: 0,
                userCallback: function(label, index, labels) {
                  // when the floored value is the same as the value we have a whole number
                  if (Math.ceil(label) === label) {
                      return label;
                  }
                }                
            },
            }]
         }       
        };

希望这会有所帮助。