Chart.js getElementsAtEvent function not recognized for onclick on bar chart - chart.js

Question

I am new to Chart.Js and facing issues on click event on bar chart. I would like to get the repective x-axis lable on click function . But I am receiving error "barchart.getElementsAtEvent is not a function at HTMLCanvasElement.Graphinit.document.getElementById.onclick". I really do not understand what exactly is wrong in my code.
I am calling the below function to generate bar chart The min, item are data array for x-axis & yaxis.
cdn : "https://cdnjs.cloudflare.com/ajax/libs/Chart.js/2.5.0/Chart.js"
var barchart;
function Graphinit(min, item, labelstring, stepcount, scaleStepWidth, reporttype, min1, item1) {
$('#myChart').remove(); // this is my <canvas> element
$('#showgraph').append(' <canvas id="myChart" width="1200" height="400"></canvas>');
inputdata = min;
xaxislabel = item;
Chart.types.Bar.extend({
name: "BarAlt",
draw: function () {
Chart.types.Bar.prototype.draw.apply(this, arguments);
var ctx = this.chart.ctx;
ctx.save();
// text alignment and color
ctx.textAlign = "center";
ctx.textBaseline = "bottom";
ctx.fillStyle = this.options.scaleFontColor;
// position
var x = this.scale.xScalePaddingLeft * 0.4;
var y = this.chart.height / 2;
// change origin
ctx.translate(x, y)
// rotate text
ctx.rotate(-90 * Math.PI / 180);
ctx.fillText(this.datasets[0].label, 0, 0);
ctx.restore();
}
});
var bridgeDataPoints = [];
if ((reporttype === "Lines picked per user") || (reporttype === "Picks per item") || (reporttype === "Lines Picked by item class") || (reporttype == "Lines picked by customer") || (reporttype == "Total Lines Picked") || reporttype == "Skipped Lines") {
for (var j = 0; j < min.length; j++) {
var dataPoint = new DataPoint1(item[j], min[j]);
bridgeDataPoints.push(dataPoint);
}
}
var data = {
labels: bridgeDataPoints,
datasets: [{
label: labelstring,
fillColor: "rgba(255, 255, 255, 1)",
strokeColor: "rgba(220,220,220,1)",
pointColor: "rgba(220,220,220,1)",
pointStrokeColor: "#fff",
pointHighlightFill: "#fff",
pointHighlightStroke: "rgba(220,220,220,1)",
data: inputdata
}]
};
var barchartoptions = {
//Boolean - If we show the scale above the chart data
scaleOverlay: false,
//Boolean - If we want to override with a hard coded scale
scaleOverride: true,
//** Required if scaleOverride is true **
//Number - The number of steps in a hard coded scale
scaleSteps: stepcount,
//Number - The value jump in the hard coded scale
scaleStepWidth: scaleStepWidth,
//Number - The scale starting value
scaleStartValue: 0,
scaleEndValue: stepcount,
//String - Colour of the scale line
scaleLineColor: "rgba(0,0,0,.1)",
//Number - Pixel width of the scale line
scaleLineWidth: 1,
//Boolean - Whether to show labels on the scale
scaleShowLabels: true,
//Interpolated JS string - can access value
scaleLabel: " <%=value%>",
//String - Scale label font declaration for the scale label
scaleFontFamily: "'Arial'",
//Number - Scale label font size in pixels
scaleFontSize: 12,
//String - Scale label font weight style
scaleFontStyle: "normal",
//String - Scale label font colour
scaleFontColor: "#666",
///Boolean - Whether grid lines are shown across the chart
scaleShowGridLines: true,
//String - Colour of the grid lines
scaleGridLineColor: "rgba(0,0,0,.05)",
//Number - Width of the grid lines
scaleGridLineWidth: 1,
//Boolean - If there is a stroke on each bar
barShowStroke: true,
//Number - Pixel width of the bar stroke
barStrokeWidth: 2,
//Number - Spacing between each of the X value sets
barValueSpacing: 10,
//Number - Spacing between data sets within X values
barDatasetSpacing: 3,
//Boolean - Whether to animate the chart
animation: true,
//Number - Number of animation steps
animationSteps: 60,
//String - Animation easing effect
animationEasing: "easeOutQuart",
//Function - Fires when the animation is complete
onAnimationComplete: function (animation) {
//alert('onAnimationComplete')
},
tooltipTemplate: "<%if (label){%><%=label.tooltip%><%}%>"
};
barchartoptions.datasetFill = false;
var ctx = $("#myChart").get(0).getContext('2d');
ctx.canvas.height = 400; // setting height of canvas
ctx.canvas.width = 1200; // setting width of canvas
//var config = Chart.defaults.bar;
barchart = new Chart(ctx).BarAlt(data, barchartoptions);
var length = inputdata.length; //min1.length;
var backgroundcolorset = [];
for (var i = 0; i < length; i++) {
var rgb = [];
for (var j = 0; j < 3; j++) {
rgb.push(Math.floor(Math.random() * 255));
}
backgroundcolorset.push('rgb(' + rgb.join(',') + ')');
}
for (var j = 0; j < length; j++) {
barchart.datasets[0].bars[j].fillColor = backgroundcolorset[j]; //bar 1
}
barchart.update();
console.log()
//console.log(barchart.getElementAtEvent(e));
document.getElementById("myChart").onclick = function (evt) {
// var activePoints =
console.log(barchart);
var activePoints = barchart.getElementsAtEvent(evt);
};
} // end Graphinit