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

Question

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!

Dorser

Here is an example an Doughnut chart with a percentage tooltip (Chart.js 4.4.0) link – Luxor

Answer 1

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">

Paff

If you have problems displaying the tooltips after that, please look into this issue and how to fix it: github.com/nnnick/Chart.js/issues/1891 – Paff

for v3, I resolved the issue by options: { plugins: { tooltip: { callbacks: { label: callbackFunction } } } } – Biron

v3 official example here chartjs.org/docs/3.5.0/configuration/tooltip.html – Buchalter

Answer 2

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 + ' €';
                }
            }

        }
    }
});

Omen

This is what I've been searching for half the day, thank you!! All other suggestions kept replacing the default text and label. – Solberg

V3 has an example of how to do this chartjs.org/docs/3.5.0/configuration/tooltip.html – Buchalter

Answer 3

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.'; }
                    }
                },
            }
        };

Demythologize

Using ChartJS 2.7.1 and the above helped me to display the Label, Value and a Symbol after many hours of searching. – Impoverish

Answer 4

This set "label + value + €"

options: {
    legend: {
        display: false
    },
    tooltips: {
        callbacks: {
            label: function(tooltipItem, data) {
                return data.labels[tooltipItem.index] + ': ' + data.datasets[tooltipItem.datasetIndex].data[tooltipItem.index] + '€';
            }
        }
    }
}

Separative

This is the only thing that worked for me. The accepted answer doesn't work for me, maybe it did work at the time... – Sachasachem

This answer works for Donut, Pie and other type of graphs like this. This should be the accepted answer I guess. – Crossfertilization

Answer 5

If you have a stacked bar chart (and I assume a stacked line chart) and you want to format all the data points included in a single bar with a currency symbol, you can do something like this:

    tooltips: {
        mode: 'label',
        callbacks: {
            label: function (tooltipItems, data) {
                return '$' + tooltipItems.yLabel;
            }
        }
    },

Note the value of mode.

If you want to have finer control of the tool tip, for example include the labels as they appear the chart's legend, you can do something like this:

    tooltips: {
        mode: 'single',  // this is the Chart.js default, no need to set
        callbacks: {
            label: function (tooltipItems, data) {
                var i, label = [], l = data.datasets.length;
                for (i = 0; i < l; i += 1) {
                    label[i] = data.datasets[i].label + ' : ' + '$' + data.datasets[i].data[tooltipItems.index];
                }
                return label;
            }
        }
    },

Mossbunker

This worked for me with a slight modification on the first code block. There's an extra 's in tooltipItem in this line return '$' + tooltipItems.yLabel. This results in no tool tips visible. – Noami

Answer 6

Just updating @Luc Lérot's answer. I had the same problem and his code helped me out but not fixed it, I had to modify it to work for me. Using Chart.js version 2.6.0

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 + ': ' + data.datasets[tooltipItems.datasetIndex].data[tooltipItems.index] + ' €';
                   }
              }

        }
    }
});

Jethro

Answer 7

As we continue our way along the release chain, the answer once again changes in Chart.js v3.X with the updated options API.

An example of adding temperature units is as follows:

const options = {
    plugins: {
        tooltip: {
            callbacks: {
                label: (item) =>
                    `${item.dataset.label}: ${item.formattedValue} °C`,
            },
        },
    },
}

Indefinite

Answer 8

To generalize code, let's use unitPrefix and unitSuffix for the datasets, for example:

datasets: [
    {
        label: 'Loss Rate',
        data: [],
        unitSuffix: "%",
    },
    {
        label: 'Price',
        data: [],
        unitPrefix: "$",
    },

Then we could have this code:

options: {
    tooltips: {
        callbacks: {
            label: function (tooltipItem, data) {
                let dataset = data.datasets[tooltipItem.datasetIndex];
                let blocks = [];
                if (dataset.label) {
                    blocks.push(${dataset.label} + ':');
                }
                if (dataset.unitPrefix) {
                    blocks.push(dataset.unitPrefix);
                }
                blocks.push(dataset.data[tooltipItem.index])
                if (dataset.unitSuffix) {
                    blocks.push(dataset.unitSuffix);
                }
                return blocks.join(' ');
            },
        },
    },
},

Siberson

Answer 9

Chart.js version 3.9.1

const options: ChartOptions = {
  plugins: {
    tooltip: {
      callbacks: {
        label: ({ label, formattedValue }) => `${label}:${formattedValue}g`
      }
    }
  }
}

Conchiolin

Answer 10

See tooltip section:

const options = {
      interaction: {
        mode: "nearest",
        intersect: false,
      },
      scales: {
        y: {
          grid: {
            display: false,
          },
          position: "right",
        },
        x: {
          ticks: {
            maxRotation: 0,
            minRotation: 0,
          },
        },
      },
      plugins: {
        legend: {
          display: false,
        },
        tooltip: {
          callbacks: {
            title: function (context) {
              return data[context[0].dataIndex].date //in title you have to call context[0] in order to get current item
            },
            label: function (context) {
              return context.raw //raw will give you the label value
            },

            intersect: false,
            backgroundColor: "#51d198",
          },
        },
      },
    }

Appease