[Chartjs]-Change the color of the legend box and the color of the x grid lines in chart.js

by

1👍

✅

To customize the legend box color you will need to use a custom HTML legend, there you can specify it with CSS, for the pink grid lines you can use the scriptable options. For both see example:

const getOrCreateLegendList = (chart, id) => {
  const legendContainer = document.getElementById(id);
  let listContainer = legendContainer.querySelector('ul');

  if (!listContainer) {
    listContainer = document.createElement('ul');
    listContainer.style.display = 'flex';
    listContainer.style.flexDirection = 'row';
    listContainer.style.margin = 0;
    listContainer.style.padding = 0;

    legendContainer.appendChild(listContainer);
  }

  return listContainer;
};

const htmlLegendPlugin = {
  id: 'htmlLegend',
  afterUpdate(chart, args, options) {
    const ul = getOrCreateLegendList(chart, options.containerID);

    // Remove old legend items
    while (ul.firstChild) {
      ul.firstChild.remove();
    }

    // Reuse the built-in legendItems generator
    const items = chart.options.plugins.legend.labels.generateLabels(chart);

    items.forEach(item => {
      const li = document.createElement('li');
      li.style.alignItems = 'center';
      li.style.cursor = 'pointer';
      li.style.display = 'flex';
      li.style.flexDirection = 'row';
      li.style.marginLeft = '10px';

      li.onclick = () => {
        const {
          type
        } = chart.config;
        if (type === 'pie' || type === 'doughnut') {
          // Pie and doughnut charts only have a single dataset and visibility is per item
          chart.toggleDataVisibility(item.index);
        } else {
          chart.setDatasetVisibility(item.datasetIndex, !chart.isDatasetVisible(item.datasetIndex));
        }
        chart.update();
      };

      // Color box
      const boxSpan = document.createElement('span');
      boxSpan.style.background = options.legendBoxColor || item.fillStyle;
      boxSpan.style.borderColor = item.strokeStyle;
      boxSpan.style.borderWidth = item.lineWidth + 'px';
      boxSpan.style.display = 'inline-block';
      boxSpan.style.height = '20px';
      boxSpan.style.marginRight = '10px';
      boxSpan.style.width = '20px';

      // Text
      const textContainer = document.createElement('p');
      textContainer.style.color = options.legendTextColor || item.fontColor;
      textContainer.style.margin = 0;
      textContainer.style.padding = 0;
      textContainer.style.textDecoration = item.hidden ? 'line-through' : '';

      const text = document.createTextNode(item.text);
      textContainer.appendChild(text);

      li.appendChild(boxSpan);
      li.appendChild(textContainer);
      ul.appendChild(li);
    });
  }
};

const options = {
  type: 'bar',
  data: {
    labels: ["Red", "Blue", "Yellow", "Green", "Purple", "Orange"],
    datasets: [{
      label: '# of Votes',
      data: [12, 19, 3, 5, 2, 3],
      borderWidth: 1,
      backgroundColor: ["Red", "Blue", "Yellow", "Green", "Purple", "Orange"]
    }]
  },
  options: {
    scales: {
      x: {
        grid: {
          color: (line) => ((line.index === 2 || line.index === 3) ? 'pink' : 'rgba(0,0,0,0.1)'),
          lineWidth: (line) => ((line.index === 2 || line.index === 3) ? 6 : 1)
        }
      }
    },
    plugins: {
      htmlLegend: {
        // ID of the container to put the legend in
        containerID: 'legendContainer',
        legendBoxColor: 'blue',
        legendTextColor: 'blue'
      },
      legend: {
        display: false,
      }
    }
  },
  plugins: [htmlLegendPlugin]
}

const ctx = document.getElementById('chartJSContainer').getContext('2d');
new Chart(ctx, options);
<body>
  <div id="legendContainer"></div>
  <canvas id="chartJSContainer" width="600" height="400"></canvas>
  <script src="https://cdnjs.cloudflare.com/ajax/libs/Chart.js/3.0.2/chart.js"></script>
</body>

Leave a comment