How to reformat tooltip in Chart.js?

Question

How to reformat tooltip in Chart.js? The chart has x-axis as time, y-axis as sales amount and tooltip to show data value for both x and y. So far tooltip can work by default but I want to change the value we see in tooltip. I can reformat the time in tooltip by redefine the tooltipFormat field in 'time'. But I don't find a similar thing for y-axis data. For example, show "$1600" instead of "Daily Ticket Sales:1600".
example tooltip format image

Could anyone tell me where should that change happen?

Could the 'custom' callback function solve problem here? Here is the code, thanks！

    var dates=data.linechart.dates;
    var times=[];
    for (var i=0; i<dates.length; i++) {
        times.push(moment(dates[i],'YYYY/MM/DD'));
    }
    // console.log(dates);
    // console.log(times);

    var salesData = {
    labels: times,

    datasets: [
        {
            label: "Daily Ticket Sales",
            fill: false,
            lineTension: 0,
            backgroundColor: "#fff",
            borderColor: "rgba(255,88,20,0.4)",
            borderCapStyle: 'butt',
            borderDash: [],
            borderDashOffset: 0.0,
            borderJoinStyle: 'miter',
            pointBorderColor: "rgba(255,88,20,0.4)",
            pointBackgroundColor: "#fff",
            pointBorderWidth: 1,
            pointHoverRadius: 5,
            pointHoverBackgroundColor: "rgba(255,88,20,0.4)",
            pointHoverBorderColor: "rgba(220,220,220,1)",
            pointHoverBorderWidth: 2,
            pointRadius: 3,
            pointHitRadius: 10,
            data: data.linechart.sales,
        }
        ]
    };


    var ctx = document.getElementById("daily_sale").getContext("2d");
    var myLineChart = new Chart(ctx, {
        type: 'line',
        data: salesData,        
        options: {

            showLines: true,
            responsive: true,
            legend:{display:false},
            tooltips:{ 
                // backgroundColor:'rgba(0,255,0,0.8)',
                custom: function(tooltip) {

                    // tooltip will be false if tooltip is not visible or should be hidden
                    if (!tooltip) { 
                        return;
                    }
                    else{
                    console.log(tooltip);
                    }   
                }
            },
            scales: 
            {
                xAxes: [{
                    type: "time",
                    time: {
                        displayFormat:'MM/DD/YY',
                        tooltipFormat: 'MM/DD/YY',
                    //     unit: 'day',
                    }
                }],
                yAxes: [{
                    ticks:{ userCallback: function(value, index, values) {
                                                // $ sign and thousand seperators
                                                return  '$'+value.toString().replace(/\B(?=(\d{3})+(?!\d))/g, ",");
                                            },  
                    },
                }],
            },
        }
    });

Answer 1

scales: {
    xAxes: [{
      type: 'time',
      time: {
          tooltipFormat:'MM/DD/YYYY', // <- HERE
          displayFormats: {
             'millisecond':'HH:mm:ss',
             'second': 'HH:mm:ss',
             'minute': 'HH:mm:ss',
             'hour': 'HH:mm:ss',
             'day': 'HH:mm:ss',
             'week': 'HH:mm:ss',
             'month': 'HH:mm:ss',
             'quarter': 'HH:mm:ss',
             'year': 'HH:mm:ss',
          }
        }
    }]
}