line chart with ChartJS

HTML

<script src="https://rawgit.com/nnnick/Chart.js/master/Chart.min.js"></script>
<canvas id="LineExt" width="600" height="300"></canvas>

JavaScript

var data = {
    labels: ['0%', '10%', '20%', '30%', '40%', '50%', '60%', '70%', '80%', '90%', '100%'],
    datasets: [{
        strokeColor: 'rgba(0, 190, 242, 1)',
        fillColor: 'rgba(177, 235, 250, 1)',
        data: [12, 30, 20, 10, 30, 50, 70, 76, 80, 90, 95]
    }]
};


var ctx = document.getElementById("LineExt").getContext("2d");
Chart.types.Line.extend({
    name: "LineExt",
    initialize: function () {
        Chart.types.Line.prototype.initialize.apply(this, arguments);

        // hide alternate x labels on the scale
        var xLabels = this.scale.xLabels;
        xLabels.forEach(function (xLabel, i) {
            if (i % 2)
                xLabels[i] = '';
        })
    },
    draw: function () {
        Chart.types.Line.prototype.draw.apply(this, arguments);

        var scale = this.scale;
        var points = this.datasets[0].points;
        var ctx = this.chart.ctx;
        var options = this.options;

        ctx.save();
        var y0 = scale.calculateY(0);
        this.options.points.forEach(function (point) {
            // linearly extrapolate y value from nearby points
            point.y = (points[Math.floor(point.xIndex)].value + points[Math.ceil(point.xIndex)].value) / 2;

            var x = scale.calculateX(point.xIndex);
            var y = scale.calculateY(point.y);

            // draw the circle
            ctx.beginPath();
            ctx.arc(x, y, 5, 0, 2 * Math.PI);
            ctx.fillStyle = point.color;
            ctx.fill();

            if (point.dropLine) {
                ctx.beginPath();
                ctx.moveTo(x, y);
                ctx.lineTo(x, y0);
                ctx.setLineDash([5, 5]);
                ctx.lineWidth = 2;
                ctx.strokeStyle = point.color;
                ctx.stroke();

                // use the same function that chart.js uses to draw the tooltip to draw our label
                var text = Chart.helpers.template(options.boxTemplate, { value: point.y })
                var...