当Chart.js中未显示数据时隐藏Y轴标签

Question

我有一个Chart.js条形图，显示了两组数据：Total SQL Queries和Slow SQL Queries。每个数据集都有Y轴标签。该图如下所示：

当我切换一组数据中的一个不显示时，仍会显示相应的Y轴标签。在解释图形时，这有点令人困惑。如下图所示：

我的问题：如何隐藏当前未显示的任何数据的Y轴标签？

这是我目前设置图表的方式：

<canvas id="SQLPerformanceChart" minHeight="400"></canvas>
<script type="text/javascript">
    ...
    var data = {
        labels: labelArray,
        datasets: [{
            label: "Total SQL Queries",
            fill: false,
            borderWidth: 1,
            borderColor: "green",
            backgroundColor: "rgba(0, 255, 0, 0.3)",
            yAxisID: "y-axis-0",
            data: totalQueriesArray
        }, {
            label: "Slow SQL Queries",
            fill: false,
            borderWidth: 1,
            borderColor: "orange",
            backgroundColor: "rgba(255, 255, 0, 0.3)",
            yAxisID: "y-axis-1",
            data: slowQueriesArray,
        }]
    };

    var options = {
        animation: false,
        scales: {
            yAxes: [{
                position: "left",
                ticks: {
                    beginAtZero: true
                },
                scaleLabel: {
                    display: true,
                    labelString: 'Total SQL Queries'
                },
                id: "y-axis-0"
            }, {
                position: "right",
                ticks: {
                    beginAtZero: true
                },
                scaleLabel: {
                    display: true,
                    labelString: 'Slow SQL Queries'
                },
                id: "y-axis-1"
            }]
        },
        tooltips: {
            enabled: true,
            mode: 'single',
            callbacks: {
                title: function(tooltipItem, data) {
                    return data.label;
                },
                beforeLabel: function(tooltipItem, data) {
                    if (tooltipItem.index == 24) {
                        return data.labels[tooltipItem.index] + " - Now";
                    } else {
                        return data.labels[tooltipItem.index] + " - " + data.labels[(tooltipItem.index) + 1];
                    }
                }
            }
        }
    }

    var ctx = document.getElementById("SQLPerformanceChart");
    var SQLPerformanceChart = new Chart(ctx, {
        type: 'bar',
        data: data,
        options: options
    });
</script>

Answer 1

您可以向图例onClick添加回调函数：

var options = {
        animation: false,
        scales: {
            yAxes: [{
                position: "left",
                ticks: {
                    beginAtZero: true
                },
                scaleLabel: {
                    display: true,
                    labelString: 'Total SQL Queries'
                },
                id: "y-axis-0"
            }, {
                position: "right",
                ticks: {
                    beginAtZero: true
                },
                scaleLabel: {
                    display: true,
                    labelString: 'Slow SQL Queries'
                },
                id: "y-axis-1"
            }]
        },
        legend: {
        onClick: function(event, legendItem) {
            //get the index of the clicked legend
            var index = legendItem.datasetIndex;
            //toggle chosen dataset's visibility
            SQLPerformanceChart.data.datasets[index].hidden = 
                !SQLPerformanceChart.data.datasets[index].hidden;
            //toggle the related labels' visibility
            SQLPerformanceChart.options.scales.yAxes[index].display =                 
                !SQLPerformanceChart.options.scales.yAxes[index].display;
            SQLPerformanceChart.update();
        }
        }
    }