Chartjs-Chart.js what is the new syntax for extending?

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2👍

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2.0 changes are explained in documentation:

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>

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