Chart.js V2: Add prefix or suffix to tooltip label

In Chart.js V1.0, I would add tooltipTemplate: "<%if (label){%><%=label %>: <%}%><%= '€' + value %>" to add a euro symbol as prefix to the tooltip label. However, this no longer works in V2. Does anybody know the new way to do accomplish this? I can't seem to find it.

Many thanks!

In the V2.0 the tooltipTemplate option is deprecated. Instead you can use callbacks to modify the displayed tooltips. There is a sample for the usage of callbacks here and you can find the possible callbacks in the documentation under Chart.defaults.global.tooltips

In your case I would do the following:

window.myLine = new Chart(chart, {
    type: 'line',
    data: lineChartData,
    options: {
            tooltips: {
                enabled: true,
                mode: 'single',
                callbacks: {
                    label: function(tooltipItems, data) { 
                        return tooltipItems.yLabel + ' €';
                    }
                }
            },
     }       
  });

Don't forget to set the HTML meta tag:

<meta charset="UTF-8">

In addition to iecs' answer, if you want to return the exact default text and add some more (like a € sign in your case), use following syntax :

var ctx = $(chartCanvas);
window.chartObject = new Chart(ctx, {
    type: 'bar',
    data: chartData,
    options: {            
        tooltips: {
            callbacks: {
                label: function(tooltipItems, data) {
                    return data.datasets[tooltipItems.datasetIndex].label +': ' + tooltipItems.yLabel + ' €';
                }
            }

        }
    }
});

See if it helps:

        var config = {
            options: {
                tooltips: {
                    callbacks: {
                        title: function (tooltipItem, data) { return data.labels[tooltipItem[0].index]; },
                        label: function (tooltipItem, data) {
                            var amount = data.datasets[tooltipItem.datasetIndex].data[tooltipItem.index];
                            var total = eval(data.datasets[tooltipItem.datasetIndex].data.join("+"));
                            return amount + ' / ' + total + ' ( ' + parseFloat(amount * 100 / total).toFixed(2) + '% )';
                        },
                        //footer: function(tooltipItem, data) { return 'Total: 100 planos.'; }
                    }
                },
            }
        };