如何将点击事件添加到图表js

Question

Hello I have a question concerning js charts. I have already created one in django application and i want to generate a javascript alert by clicking a certain point in the chart. How can the alert get the value of the point that i choose? For example with the value 92 like what is shown in the figure below:

Answer 1

This can be done with an onClick even handler as follows:

onClick: (event, elements, chart) => {
  if (elements[0]) {            
     const i = elements[0].index;
     alert(chart.data.labels[i] + ': ' + chart.data.datasets[0].data[i]);
  }
}

Please take a look at below runnable code and see how it works.

 new Chart('myChart', { type: 'line', data: { labels: ["January", "February", "March", "April", "May", "June", "July"], datasets: [{ label: '# of Votes', data: [65, 59, 80, 81, 56, 55, 40], borderColor: '#a00' }] }, options: { onClick: (event, elements, chart) => { if (elements[0]) { const i = elements[0].index; alert(chart.data.labels[i] + ': ' + chart.data.datasets[0].data[i]); } } } });

 <script src="https://cdnjs.cloudflare.com/ajax/libs/Chart.js/3.7.1/chart.min.js"></script> <canvas id="myChart" width="400" height="95"></canvas>