title: Draw horizontal lines in Chart.js 2.0
body: <p>Can you help me how to extend Chart.js v2.0. I need to draw some horizontal lines in the charts, something similar to: <a href="http://jsfiddle.net/vsh6tcfd/3/" rel="noreferrer">http://jsfiddle.net/vsh6tcfd/3/</a></p>
  
  <pre><code>var originalLineDraw = Chart.controllers.bar.prototype.draw;
  
  Chart.helpers.extend(Chart.controllers.bar.prototype, {
    draw: function() {
      originalLineDraw.apply(this, arguments);
  
      var chart = this.chart;
      var ctx = chart.chart.ctx;
  
      var index = chart.config.data.lineAtIndex;
      if (index) {
        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.left);
        ctx.strokeStyle = '#ff0000';
        ctx.lineTo(xaxis.getPixelForValue(undefined, index), yaxis.right);
        ctx.stroke();
        ctx.restore();
      }
    }
  });
  
  var config = {
      type: type,
      data:  jQuery.extend(true, {}, data),
      options: this.chartdata.options,
      lineAtIndex: 2
  };
  
  new Chart(ctx, config);  
  </code></pre>