ChartJS 多个 X 轴和 y 轴上的额外标签答案

【问题标题】：ChartJS multiple X axis and extra labels in y axisChartJS 多个 X 轴和 y 轴上的额外标签
【发布时间】：2021-05-31 20:43:51
【问题描述】：

我有一个使用 ChartJS 最新版本 3.3.2 的图表。我的代码如下：

<html lang="en">
    <head>
        <meta charset="utf-8">
        <meta name="viewport" content="width=device-width, initial-scale=1.0">
        <meta name="description" content="">
        <meta name="author" content="">
        <title>OCA-Test</title>
        <script src="https://cdnjs.cloudflare.com/ajax/libs/Chart.js/3.3.2/chart.min.js"></script>
    </head>
    <body>
        <canvas id="chartJSContainer"></canvas>
        <script>
const labels = ["A","B","C","D","E","F","G","H","I","J"];
const data = {
  labels: labels,
  datasets: [
    {
      label: 'Dataset 1',
      data: [-92, -100, -99, -86, 8, 56, -94, -89, -92, -24],
      borderColor: 'transparent',
      backgroundColor: 'transparent',
      order: 1
    },
    {
      label: 'Dataset 2',
      data: [-92, -100, -99, -86, 8, 56, -94, -89, -92, -24],
      borderColor: 'black',
      backgroundColor: 'blue',
      type: 'line',
      order: 0
    }
  ]
};
const config = {
  type: 'bar',
  data: data,
  options: {
    responsive: true,
    plugins: {
      legend: {
        display: false
      },
      title: {
        display: false
      }
    },
    scales: {
      y: {
        min: -100,
        max: 100
      }
    }
  }
};
var chart = new Chart(document.getElementById('chartJSContainer'), config);
        </script>
    </body>
</html>

如何在图表顶部添加相同的 x 轴标签，并在图表左侧添加新标签。见附件捕获。谢谢。

What I'm looking for

【问题讨论】：

标签： chart.js

【解决方案1】：

对于顶部的 X 轴，您可以添加另一个 X 轴并将位置设置为顶部，对于 Y 轴之间的标签，最好为此编写一个自定义插件。

例子：

var options = {
  type: 'line',
  data: {
    labels: ["A", "B", "C", "D", "E", "F"],
    datasets: [{
        label: '# of Votes',
        data: [12, 19, 3, 5, 2, 3],
        borderWidth: 1
      },
      {
        label: '# of Points',
        data: [7, 11, 5, 8, 3, 7],
        borderWidth: 1
      }
    ]
  },
  options: {
    scales: {
      x: {
        position: 'bottom',
        grid: {
          offset: true // offset true to get labels in between the lines instead of on the lines
        }
      },
      x2: {
        position: 'top',
        grid: {
          offset: true // offset true to get labels in between the lines instead of on the lines
        }
      },
      y: {
        ticks: {
          count: (context) => (context.scale.chart.data.labels.length + 1)
        }
      }
    },
    plugins: {
      labelsY: {
        font: 'Arial',
        size: '14px',
        color: '#666',
        align: 'right',
        reverseLabels: false // true to make A start at top and F at bottom
      }
    }
  },
  plugins: [{
    id: 'labelsY',
    afterDraw: (chart, args, options) => {
      const {
        ctx,
        scales: {
          y,
          x
        },
        data: {
          labels
        }
      } = chart;

      let dupLabels = JSON.parse(JSON.stringify(labels)); // remove pointer to internal labels array so you dont get glitchy behaviour

      if (options.reverseLabels) {
        dupLabels = dupLabels.reverse();
      }

      dupLabels.forEach((label, i) => {
        ctx.save();

        ctx.textAlign = options.align || 'right';
        ctx.font = `${options.size || '20px'} ${options.font || 'Arial'}`;
        ctx.fillStyle = options.color || 'black'

        let xPos = x.getPixelForValue(labels[0]) - ctx.measureText(label).width;
        let yPos = (y.getPixelForValue(y.ticks[i].value) + y.getPixelForValue(y.ticks[i + 1].value)) / 2;

        ctx.fillText(label, xPos, yPos)

        ctx.restore();
      });
    }
  }]
}

var ctx = document.getElementById('chartJSContainer').getContext('2d');
new Chart(ctx, options);

<body>
  <canvas id="chartJSContainer" width="600" height="400"></canvas>
  <script src="https://cdnjs.cloudflare.com/ajax/libs/Chart.js/3.3.0/chart.js"></script>
</body>

【讨论】：

非常感谢！