title: How to get date label of line Chart?
body: <p>I use line of Chart.js( Version: 2.7.2 ) in my application and I open dialog  when clicking on some element and
  I need to get label(date on xAxes) of the current element. Googling I found examples and trying to make as next :</p>
  
  <pre><code>        var lineCanvas = document.getElementById("canvasVotesByDays");
          var ctx = lineCanvas.getContext('2d');
  
          var lineChart = new Chart(ctx, {
              type: 'line',
              data: {
                  labels: monthsXCoordItems,
                  datasets: [
                      {
                          label: 'Correct Votes',
                  ...
  
          lineCanvas.onclick = function (e) {
              console.log("INSIDE lineChart::")
              console.log(lineChart)
  
              var slice = lineChart.getPointsAtEvent(e);
              ...
  </code></pre>
  
  <p>But on the last line I got error :</p>
  
  <pre><code>Uncaught TypeError: lineChart.getPointsAtEvent is not a function
      at HTMLCanvasElement.lineCanvas.onclick 
  </code></pre>
  
  <p>In the console I see the propeerties of the lineChart object:
  <a href="https://imgur.com/a/E7jsoBc" rel="noreferrer">https://imgur.com/a/E7jsoBc</a></p>
  
  <p>Why error and how to get label property?</p>
  
  <p>Thank you!</p>