How get sum of total values in stackedBar ChartJs

Question

I'm trying to get the sum of all values of a stackedBar and include this total in tooltip.

Note: my datasets aren't static, this is an example

var barChartData = {
        labels: ["January", "February", "March", "April", "May", "June", "July"],
        datasets: [{
            label: 'Corporation 1',
            backgroundColor: "rgba(220,220,220,0.5)",
            data: [50, 40, 23, 45, 67, 78, 23]
        }, {
            label: 'Corporation 2',
            backgroundColor: "rgba(151,187,205,0.5)",
            data: [50, 40, 78, 23, 23, 45, 67]
        }, {
            label: 'Corporation 3',
            backgroundColor: "rgba(151,187,205,0.5)",
            data: [50, 67, 78, 23, 40, 23, 55]
        }]

    };

    window.onload = function() {
        var ctx = document.getElementById("canvas").getContext("2d");
        window.myBar = new Chart(ctx, {
            type: 'bar',
            data: barChartData,
            options: {
                title:{
                    display:true,
                    text:"Chart.js Bar Chart - Stacked"
                },
                tooltips: {
                    mode: 'label',
                    callbacks: {
                       label: function(tooltipItem, data) {
                       var corporation = data.datasets[tooltipItem.datasetIndex].label;
                       var valor = data.datasets[tooltipItem.datasetIndex].data[tooltipItem.index];
                       var total = eval(data.datasets[tooltipItem.datasetIndex].data.join("+"));
                       return total+"--"+ corporation +": $" + valor.toFixed(2).replace(/(\d)(?=(\d{3})+\.)/g, '$1,');
                  }
                    }
                },
                responsive: true,
                scales: {
                    xAxes: [{
                        stacked: true,
                    }],
                    yAxes: [{
                        stacked: true
                    }]
                }
            }
        });
    };

Now total is the sum per dataset and I need the sum per stackedBar.

Example

Label A: value A

Label B: value B

Label C: value C

TOTAL: value A + value B + value C

It is possible to get that total value?

Thanks, Idalia.

Answer 1

First you should know that if you return an array instead of a single string in the callback of the tooltip, it will display all the strings in your array as if it were different datasets (see this answer for more details).

So I edited a little bit your callback to the following:

callbacks: {
    label: function(tooltipItem, data) {
        var corporation = data.datasets[tooltipItem.datasetIndex].label;
        var valor = data.datasets[tooltipItem.datasetIndex].data[tooltipItem.index];

        // Loop through all datasets to get the actual total of the index
        var total = 0;
        for (var i = 0; i < data.datasets.length; i++)
            total += data.datasets[i].data[tooltipItem.index];

        // If it is not the last dataset, you display it as you usually do
        if (tooltipItem.datasetIndex != data.datasets.length - 1) {
            return corporation + " : $" + valor.toFixed(2).replace(/(\d)(?=(\d{3})+\.)/g, '$1,');
        } else { // .. else, you display the dataset and the total, using an array
            return [corporation + " : $" + valor.toFixed(2).replace(/(\d)(?=(\d{3})+\.)/g, '$1,'), "Total : $" + total];
        }
    }
}

You can see the full code in this jsFiddle, and here is its result :