每次从下拉列表中选择项目时，如何使图表动态化？

Question

after I click on one of the items in my dropdown you can see that it loads dynamically. However, after it has first loaded it does not load anymore. My goal is to make it completely dynamic here. Do you have an idea how I can make it happen?

const ctx = document.getElementById('jobChart').getContext('2d')
const chart = new Chart(ctx, {
  type: 'line',
  data: {
    labels: ["1", "2", "3", "4", "5", "6", "7", "8", "9+"],
    datasets: []
  },
});

const jobDatasets = {
  backend: [{
    label: "10th Percentile",
    borderColor: "#c4c1ff",
    backgroundColor: "#c4c1ff",
    data: [0, 10, 5, 2, 20, 30, 45, 33, 67]
  }, {
    label: "25th Percentile",
    borderColor: "#645bff",
    backgroundColor: "#645bff",
    data: [5, 12, 14, 15, 19, 31, 55, 61, 62]
  }],
  frontend: [{
    label: "10th Percentile",
    borderColor: "#c4c1ff",
    backgroundColor: "#c4c1ff",
    data: [35, 11, 49, 45, 55, 47, 5, 62, 1]
  }, {
    label: "25th Percentile",
    borderColor: "#645bff",
    backgroundColor: "#645bff",
    data: [10, 31, 48, 49, 59, 65, 67, 76, 12]
  }],
  fullstack: [{
    label: "10th Percentile",
    borderColor: "#c4c1ff",
    backgroundColor: "#c4c1ff",
    data: [11, 37, 10, 27, 62, 52, 8, 19, 24]
  }, {
    label: "25th Percentile",
    borderColor: "#645bff",
    backgroundColor: "#645bff",
    data: [8, 25, 28, 30, 38, 45, 58, 62, 74]
  }]
}

document.getElementById('job-role').addEventListener('change', function() {
  chart.data.datasets = jobDatasets[this.value]
  chart.update()
});

Answer 1

Your code looks fine. I just added an empty option that reflects the initial state of the chart where no data is displayed yet. Accordingly I changed the event listener on the select element as follows:

document.getElementById('job-role').addEventListener('change', function() {
  chart.data.datasets = this.value == 'none' ? [] : jobDatasets[this.value];
  chart.update();
});

Please take a look at your amended code and see how it works.

 const chart = new Chart('jobChart', { type: 'line', data: { labels: ["1", "2", "3", "4", "5", "6", "7", "8", "9+"], datasets: [] }, }); const jobDatasets = { backend: [{ label: "10th Percentile", borderColor: "#c4c1ff", backgroundColor: "#c4c1ff", data: [0, 10, 5, 2, 20, 30, 45, 33, 67] }, { label: "25th Percentile", borderColor: "#645bff", backgroundColor: "#645bff", data: [5, 12, 14, 15, 19, 31, 55, 61, 62] }], frontend: [{ label: "10th Percentile", borderColor: "#c4c1ff", backgroundColor: "#c4c1ff", data: [35, 11, 49, 45, 55, 47, 5, 62, 1] }, { label: "25th Percentile", borderColor: "#645bff", backgroundColor: "#645bff", data: [10, 31, 48, 49, 59, 65, 67, 76, 12] }], fullstack: [{ label: "10th Percentile", borderColor: "#c4c1ff", backgroundColor: "#c4c1ff", data: [11, 37, 10, 27, 62, 52, 8, 19, 24] }, { label: "25th Percentile", borderColor: "#645bff", backgroundColor: "#645bff", data: [8, 25, 28, 30, 38, 45, 58, 62, 74] }] }; document.getElementById('job-role').addEventListener('change', function() { chart.data.datasets = this.value == 'none'? []: jobDatasets[this.value]; chart.update(); });

 <script src="https://cdnjs.cloudflare.com/ajax/libs/Chart.js/2.9.4/Chart.min.js"></script> <b>Chart Type</b> <select id="job-role"> <option value="none"></option> <option value="backend">Backend Engineer</option> <option value="frontend">Frontend Engineer</option> <option value="fullstack">Fullstack Engineer</option> </select> <div style="position: relative; width:85vw"> <canvas id="jobChart" height="110"></canvas> </div>