nnnick chart.js - Custom Tooltip on Line Chart - chart.js

Question

We are using nnnick chart.js (open source chart) in our application for reporting purpose.There is a requirement to show the Custom tool-tip in the line chart.
As of now , Normal chart tooltip is showing based on the X-axis and Y axis dataset values. But Here we want to show the Dynamic additional data in the Tooltip.
For Example ,
Let us take a Student Enrollment .
here
X Axis Value - Enrollment Month (Jan,Feb,Mar....etc)
Y Axis Value - Number of Enrollments (10,20,30...ect)
After the Line chart is plotted , Now it is displaying (Jan ,10) in the tooltip.
We have to show the Number of Male & Female student details in the tool tip On mouse over the data point Jan 10 (i.e) (Jan,10, Male:5 , Female 5 ).
If you see the above screen shot , Green color is toop-tip is the normal one which is a built-in option. Red Color highlighted tool-tip is the one we are expecting.
Please provide any suggestion on this .

Answer 1

So you can achieve this using the custom tool tip function in the newer (not sure when it was included) version of chart js. You can have it display anything you want in place of a normal tooltip so in this case i have added a tooltip and a tooltip-overview.
The really annoying thing is though in this function you are not told which index you are currently showing a tooltip for. Two ways to solve this, override the showToolTip function so it actually passes this information or do a quick little hack to extract the label from the tooltip text and get the index from the labels array (hacky but quicker so i went for this one in the example)
So here is a quick example based upon the samples in chartjs samples folder. This is just a quick example so you would prob need to play around with the positioning and stuff until its what you need.
Chart.defaults.global.pointHitDetectionRadius = 1;
Chart.defaults.global.customTooltips = function(tooltip) {
// Tooltip Element
var tooltipEl = $('#chartjs-tooltip');
var tooltipOverviewEl = $('#chartjs-tooltip-overview');
// Hide if no tooltip
if (!tooltip) {
tooltipEl.css({
opacity: 0
});
tooltipOverviewEl.css({
opacity: 0
});
return;
}
//really annoyingly we don;t get told which index this comes from so going to have
//to extract the label from the text :( and then find the index based on that
//other option here is to override the the whole showTooltip in chartjs and have the index passed
var label = tooltip.text.substr(0, tooltip.text.indexOf(':'));
var labelIndex = labels.indexOf(label);
var maleEnrolmentNumber = maleEnrolments[labelIndex];
var femaleEnrolmentNumber = FemaleEnrolments[labelIndex];
// Set caret Position
tooltipEl.removeClass('above below');
tooltipEl.addClass(tooltip.yAlign);
// Set Text
tooltipEl.html(tooltip.text);
//quick an ddirty could use an actualy template here
var tooltipOverviewElHtml = "<div> Overall : " + (maleEnrolmentNumber + femaleEnrolmentNumber) + "</div>";
tooltipOverviewElHtml += "<div> Male : " + (maleEnrolmentNumber) + "</div>";
tooltipOverviewElHtml += "<div> Female : " + (femaleEnrolmentNumber) + "</div>";
tooltipOverviewEl.html(tooltipOverviewElHtml);
// Find Y Location on page
var top;
if (tooltip.yAlign == 'above') {
top = tooltip.y - tooltip.caretHeight - tooltip.caretPadding;
} else {
top = tooltip.y + tooltip.caretHeight + tooltip.caretPadding;
}
// Display, position, and set styles for font
tooltipEl.css({
opacity: 1,
left: tooltip.chart.canvas.offsetLeft + tooltip.x + 'px',
top: tooltip.chart.canvas.offsetTop + top + 'px',
fontFamily: tooltip.fontFamily,
fontSize: tooltip.fontSize,
fontStyle: tooltip.fontStyle,
});
tooltipOverviewEl.css({
opacity: 1,
fontFamily: tooltip.fontFamily,
fontSize: tooltip.fontSize,
fontStyle: tooltip.fontStyle,
});
};
var maleEnrolments = [5, 20, 15, 20, 20, 30, 50]; // Integer array for male each value is corresponding to each month
var FemaleEnrolments = [5, 0, 15, 20, 30, 30, 20]; // Integer array for Female each value is corresponding to each month
var labels = ["Jan", "February", "March", "April", "May", "June", "July"]; //Enrollment by Month
var lineChartData = {
labels: labels,
datasets: [{
label: "Student Details",
fillColor: "rgba(151,187,205,0.2)",
strokeColor: "rgba(151,187,205,1)",
pointColor: "rgba(151,187,205,1)",
pointStrokeColor: "#fff",
pointHighlightFill: "#fff",
pointHighlightStroke: "rgba(151,187,205,1)",
data: [10, 20, 30, 40, 50, 60, 70], //enrollement Details overall (Male + Female)
}]
};
var ctx2 = document.getElementById("chart2").getContext("2d");
window.myLine = new Chart(ctx2).Line(lineChartData, {
responsive: true
});
#canvas-holder1 {
width: 300px;
margin: 20px auto;
}
#canvas-holder2 {
width: 50%;
margin: 20px 25%;
position:relative;
}
#chartjs-tooltip-overview {
opacity: 0;
position: absolute;
background: rgba(0, 0, 0, .7);
color: white;
padding: 3px;
border-radius: 3px;
-webkit-transition: all .1s ease;
transition: all .1s ease;
pointer-events: none;
-webkit-transform: translate(-50%, 0);
transform: translate(-50%, 0);
left:200px;
top:0px
}
#chartjs-tooltip {
opacity: 1;
position: absolute;
background: rgba(0, 0, 0, .7);
color: white;
padding: 3px;
border-radius: 3px;
-webkit-transition: all .1s ease;
transition: all .1s ease;
pointer-events: none;
-webkit-transform: translate(-50%, 0);
transform: translate(-50%, 0);
}
.chartjs-tooltip-key {
display:inline-block;
width:10px;
height:10px;
}
<script src="https://raw.githack.com/nnnick/Chart.js/master/Chart.js"></script>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<div id="canvas-holder2">
<div id="chartjs-tooltip-overview"></div>
<div id="chartjs-tooltip"></div>
<canvas id="chart2" width="600" height="600" />
</div>