javascript - Chart.js 的新扩展语法是什么？

Question

因此，在查看 Chart.js 的一些代码示例时，我遇到了以下 JSFiddle ( http://jsfiddle.net/dbyze2ga/14/ )。当我将其复制到我的 IDE (brackets.io) 时，它不起作用，直到我意识到这个 jsfiddle 使用 Chart.js 1.x.x。

使用 v2.0 扩展图表的当前语法是什么？我尝试检查文档；但老实说，这让我更加困惑。没有帮助，至少在括号的情况下，它不会显示图表的任何真正有用的点完成。

有问题的 JS 代码是:

var data = {
    labels: ["JAN", "FEB", "MAR", "APR", "MAY", "JUN", "JUL", "AUG", "SEP", "OCT", "NOV", "DEC"],
    datasets: [{
        data: [12, 3, 2, 1, 8, 8, 2, 2, 3, 5, 7, 1]
    }]
};

var ctx = document.getElementById("LineWithLine").getContext("2d");

Chart.types.Line.extend({
    name: "LineWithLine",
    draw: function () {
        Chart.types.Line.prototype.draw.apply(this, arguments);

        var point = this.datasets[0].points[this.options.lineAtIndex]
        var scale = this.scale

        // draw line
        this.chart.ctx.beginPath();
        this.chart.ctx.moveTo(point.x, scale.startPoint + 24);
        this.chart.ctx.strokeStyle = '#ff0000';
        this.chart.ctx.lineTo(point.x, scale.endPoint);
        this.chart.ctx.stroke();

        // write TODAY
        this.chart.ctx.textAlign = 'center';
        this.chart.ctx.fillText("TODAY", point.x, scale.startPoint + 12);
    }
});

new Chart(ctx).LineWithLine(data, {
    datasetFill : false,
    lineAtIndex: 2
});

Answer 1

2.0 的变化在 documentation 中有解释。 :

var myLineExtend = Chart.controllers.line.prototype.draw;

var ctx = document.getElementById("LineWithLine").getContext("2d");

var config = {
  type: 'line',
  data: {
    labels: ["JAN", "FEB", "MAR", "APR", "MAY", "JUN", "JUL", "AUG", "SEP", "OCT", "NOV", "DEC"],
    datasets: [{
      data: [12, 3, 2, 1, 8, 8, 2, 2, 3, 5, 7, 1]
    }],
    datasetFill : false,
    lineAtIndex: 2
  }
};

Chart.helpers.extend(Chart.controllers.line.prototype, {
    draw: function () {
    
      myLineExtend.apply(this, arguments);   

      var chart = this.chart;
      var ctx = chart.chart.ctx;

      var index = chart.config.data.lineAtIndex;
      var xaxis = chart.scales['x-axis-0'];
      var yaxis = chart.scales['y-axis-0'];

      ctx.save();
      ctx.beginPath();
      ctx.moveTo(xaxis.getPixelForValue(undefined, index), yaxis.top + 24);
      ctx.strokeStyle = '#ff0000';
      ctx.lineTo(xaxis.getPixelForValue(undefined, index), yaxis.bottom);
      ctx.stroke();
      ctx.restore();

      ctx.textAlign = 'center';
      ctx.fillText("TODAY", xaxis.getPixelForValue(undefined, index), yaxis.top + 12);

    }
});

new Chart(ctx, config);

<script src="https://github.com/chartjs/Chart.js/releases/download/v2.6.0/Chart.bundle.min.js"></script>
<canvas id="LineWithLine"></canvas>