我试图做一个按钮，清除/破坏画布上的图表，这样我就可以在同一个画布上做一个新的，但我一直得到我的函数被声明，但它的值从来没有读。我该如何解决这个问题？我将分享我的很多代码下，这样它更容易帮助我，但代码混乱。
于飞：

<!--Canvas for chart-->
        <canvas id="chart"></canvas>
        <!-- https://www.chartjs.org/docs/latest/ -->
        <script id="graph1" type="text/JavaScript" src="js/Main.js"></script>     

        <button type="button" id="generate" onclick="generateGraph()">Generate</button>
        <button type="button" id="clear" onclick="clearCanvas()">Clear</button>

JavaScript语言：

//Url for JSON-file
var url = "";
//The labels for the chart
var graphLabels = [];

var generateButton = document.getElementById("generate");

//When a checkbox is checked (function)
function generateGraph(url) {
  var arrayTheta = [];
  var arrayRange = [];
  var mcsArray = [];
  var channelArray = [];

  //Getting the data from json-file (function) {NOTE: gotta figure out a way to get data from multible JSON-files}
  async function getData(arrayRange, arrayTheta, url, graphLabels, mcsArray, channelArray) {  

    //Gets data from the JSON-file, were the url is the box that is checked
    const response = await fetch(url);
    const productData = await response.json();

    for (let index = 0; index < productData.length; index++) {
      arrayTheta.push(productData[index].theta);
      arrayRange.push(productData[index].Range);
    }

    //The graph, copied from Chart.js, but changed for our prefrence
    const ctx = document.getElementById('chart').getContext('2d');
    const myChart = new Chart(ctx,{
        type: 'line',
        data: {
            labels: arrayTheta,
            datasets: [{
                label: graphLabels,
                data: arrayRange,
                backgroundColor: 'rgba(255, 99, 132, 0.2)',

                borderColor: 'rgba(255, 99, 132, 1)',
                pointRadius: 0,
                tension: 0.4
            }]
        },
        options: {
            scales: {
                y: {
                    beginAtZero: true
                }
                ,x: {
                  display: true,
                  type: 'linear'
                }
            }
        }
    });

  }

  getData(arrayRange, arrayTheta, url, graphLabels, mcsArray, channelArray)

  //Trying to make a clear button, but does not work (Remove this comment when it works)
  var clearButton = document.getElementById("clear")

  function clearCanvas() {
    console.log("DETROYINGG")
    myChart.destroy()

  }
}

我希望这个代码足以帮助我，但如果你需要更多，我也可以发送。