[Chartjs]-Chart.js Bar and Line chart

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, 0), yaxis.getPixelForValue(70));
      ctx.strokeStyle = '#000000';
      ctx.lineTo(xaxis.getPixelForValue(undefined, 7), yaxis.getPixelForValue(10));
      ctx.stroke();
      ctx.restore();
    }
  }
});

var config = {
  type: 'bar',
  data: {
    labels: ["January", "February", "March", "April", "May", "June", "July"],
    datasets: [{
      label: "My First dataset",
      data: [65, 0, 80, 81, 56, 85, 40],
      fill: false
    }],
    lineAtIndex: 2
  }
};

var ctx = document.getElementById("myChart").getContext("2d");
new Chart(ctx, config);

<script src="https://cdnjs.cloudflare.com/ajax/libs/Chart.js/2.0.0-beta/Chart.js"></script>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<canvas id="myChart"></canvas>