如何通过多个图获取label onclick事件

Question

我有一个正在工作的chart.jshttps://www.flottefeger.ch/charts.html我正在尝试使用chart.js将一个点击事件添加到我的折线图中。我可以提醒弹出两个值。但我还需要一个参数。数据集中标签中的那些。

看起来是这样的：

但现在我的问题是，如何获得我点击的图形？我是说标签上的价值？

在我的例子中，它可能是Timmy或Siri

var ctx = document.getElementById("myChart").getContext('2d');
var myChart = new Chart(ctx, {
type: 'line',
data: {
labels: ["Red", "Blue", "Yellow", "Green", "Purple", "Orange"],
datasets: [{
label: 'Timmy',
data: [12, 19, 3, 5, 2, 3],
backgroundColor: [
'rgba(255, 99, 132, 0.2)',
'rgba(54, 162, 235, 0.2)',
'rgba(255, 206, 86, 0.2)',
'rgba(75, 192, 192, 0.2)',
'rgba(153, 102, 255, 0.2)',
'rgba(255, 159, 64, 0.2)'
],
borderColor: [
'rgba(255,99,132,1)',
'rgba(54, 162, 235, 1)',
'rgba(255, 206, 86, 1)',
'rgba(75, 192, 192, 1)',
'rgba(153, 102, 255, 1)',
'rgba(255, 159, 64, 1)'
],
borderWidth: 1
},
{
label: 'Siri',
data: [24, 38, 6, 10, 4, 6],
backgroundColor: [
'rgba(255, 99, 132, 0.2)',
'rgba(54, 162, 235, 0.2)',
'rgba(255, 206, 86, 0.2)',
'rgba(75, 192, 192, 0.2)',
'rgba(153, 102, 255, 0.2)',
'rgba(255, 159, 64, 0.2)'
],
borderColor: [
'rgba(255,99,132,1)',
'rgba(54, 162, 235, 1)',
'rgba(255, 206, 86, 1)',
'rgba(75, 192, 192, 1)',
'rgba(153, 102, 255, 1)',
'rgba(255, 159, 64, 1)'
],
borderWidth: 1
},

]
},
options: {
scales: {
yAxes: [{
ticks: {
beginAtZero: true
}
}]
}
},

});
/* https://github.com/chartjs/Chart.js/issues/2292 */
document.getElementById("myChart").onclick = function(evt) {
var activePoints = myChart.getElementsAtEventForMode(evt, 'point', myChart.options);
var firstPoint = activePoints[0];
var label = myChart.data.labels[firstPoint._index];
var value = myChart.data.datasets[firstPoint._datasetIndex].data[firstPoint._index];
alert(label + ": " + value);
};

<script src="https://cdnjs.cloudflare.com/ajax/libs/Chart.js/2.7.2/Chart.bundle.js"></script>
<h1>chart.js, click on data demo</h1>
<canvas id="myChart"></canvas>

Answer 1

您可以按如下方式更改onclick函数：

document.getElementById("myChart").onclick = function(evt) {
const datasetIndex = myChart.getElementAtEvent(event)[0]._datasetIndex;
if (datasetIndex >= 0) {
...
alert(myChart.data.datasets[datasetIndex].label + 'n' + label + ": " + value);
}
};

请看一下您修改后的代码，看看它是如何工作的。

var ctx = document.getElementById("myChart").getContext('2d');
var myChart = new Chart(ctx, {
type: 'line',
data: {
labels: ["Red", "Blue", "Yellow", "Green", "Purple", "Orange"],
datasets: [{
label: 'Timmy',
data: [12, 19, 3, 5, 2, 3],
backgroundColor: [
'rgba(255, 99, 132, 0.2)',
'rgba(54, 162, 235, 0.2)',
'rgba(255, 206, 86, 0.2)',
'rgba(75, 192, 192, 0.2)',
'rgba(153, 102, 255, 0.2)',
'rgba(255, 159, 64, 0.2)'
],
borderColor: [
'rgba(255,99,132,1)',
'rgba(54, 162, 235, 1)',
'rgba(255, 206, 86, 1)',
'rgba(75, 192, 192, 1)',
'rgba(153, 102, 255, 1)',
'rgba(255, 159, 64, 1)'
],
borderWidth: 1
},
{
label: 'Siri',
data: [24, 38, 6, 10, 4, 6],
backgroundColor: [
'rgba(255, 99, 132, 0.2)',
'rgba(54, 162, 235, 0.2)',
'rgba(255, 206, 86, 0.2)',
'rgba(75, 192, 192, 0.2)',
'rgba(153, 102, 255, 0.2)',
'rgba(255, 159, 64, 0.2)'
],
borderColor: [
'rgba(255,99,132,1)',
'rgba(54, 162, 235, 1)',
'rgba(255, 206, 86, 1)',
'rgba(75, 192, 192, 1)',
'rgba(153, 102, 255, 1)',
'rgba(255, 159, 64, 1)'
],
borderWidth: 1
},
]
},
options: {
scales: {
yAxes: [{
ticks: {
beginAtZero: true
}
}]
}
},
});
document.getElementById("myChart").onclick = function(evt) {
const datasetIndex = myChart.getElementAtEvent(event)[0]._datasetIndex;
if (datasetIndex >= 0) {
var activePoints = myChart.getElementsAtEventForMode(evt, 'point', myChart.options);
var firstPoint = activePoints[0];
var label = myChart.data.labels[firstPoint._index];
var value = myChart.data.datasets[firstPoint._datasetIndex].data[firstPoint._index];
alert(myChart.data.datasets[datasetIndex].label + 'n' + label + ": " + value);
}
};

<script src="https://cdnjs.cloudflare.com/ajax/libs/Chart.js/2.9.4/Chart.min.js"></script>
<canvas id="myChart"></canvas>