#グラフ領域の境界線

const config = {
  type: 'line',
  data: data,
  options: {
    plugins: {
      chartAreaBorder: {
        borderColor: 'red',
        borderWidth: 2,
        borderDash: [5, 5],
        borderDashOffset: 2,
      }
    }
  },
  plugins: [chartAreaBorder]
};

const chartAreaBorder = {
  id: 'chartAreaBorder',
  beforeDraw(chart, args, options) {
    const {ctx, chartArea: {left, top, width, height}} = chart;
    ctx.save();
    ctx.strokeStyle = options.borderColor;
    ctx.lineWidth = options.borderWidth;
    ctx.setLineDash(options.borderDash || []);
    ctx.lineDashOffset = options.borderDashOffset;
    ctx.strokeRect(left, top, width, height);
    ctx.restore();
  }
};

const DATA_COUNT = 7;
const NUMBER_CFG = {count: DATA_COUNT, min: -100, max: 100};
const labels = Utils.months({count: 7});
const data = {
  labels: labels,
  datasets: [
    {
      label: 'Dataset 1',
      data: Utils.numbers(NUMBER_CFG),
      borderColor: Utils.CHART_COLORS.red,
      backgroundColor: Utils.transparentize(Utils.CHART_COLORS.red, 0.5),
    },
    {
      label: 'Dataset 2',
      data: Utils.numbers(NUMBER_CFG),
      borderColor: Utils.CHART_COLORS.blue,
      backgroundColor: Utils.transparentize(Utils.CHART_COLORS.blue, 0.5),
    }
  ]
};