charts.js

let chart;

const buildChartData = (data, casesType) => {
    let chartData = [];
    let lastDataPoint;
    for(let date in data.cases){
        if(lastDataPoint){
            let newDataPoint = {
                x: date,
                y: data[casesType][date] - lastDataPoint
            }
            chartData.push(newDataPoint);
        }
        lastDataPoint = data[casesType][date];
    }
    return chartData;
}

const updateData = (data, borderColor, backgroundColor) => {
    chart.data.datasets[0].data = data;
    chart.data.datasets[0].borderColor = borderColor;
    chart.data.datasets[0].backgroundColor = backgroundColor;
    chart.update({
        duration: 800,
        easing: 'easeInOutCubic'
    });
}

const buildChart = (chartData) => {
    var timeFormat = 'MM/DD/YY';
    var ctx = document.getElementById('myChart').getContext('2d');
    chart = new Chart(ctx, {
        // The type of chart we want to create
        type: 'line',

        // The data for our dataset
        data: {
            datasets: [{
                backgroundColor: 'rgba(204, 16, 52, 0.5)',
                borderColor: '#CC1034',
                data: chartData
            }]
        },

        // Configuration options go here
        options: {
            legend: {
                display: false
            },
            elements: {
                point:{
                    radius: 0
                }
            },
            maintainAspectRatio: false,
            tooltips: {
                mode: 'index',
                intersect: false,
                callbacks: {
                    label: function(tooltipItem, data) {
                        return numeral(tooltipItem.value).format('+0,0');
                    }
                }
            },
            scales:     {
                xAxes: [{
                    type: "time",
                    time: {
                        format: timeFormat,
                        tooltipFormat: 'll'
                    }
                }],
                yAxes: [{
                    gridLines: {
                        display:false
                    },
                    ticks: {
                        // Include a dollar sign in the ticks
                        callback: function(value, index, values) {
                            return numeral(value).format('0a');
                        }
                    }
                }]
            }
        }
    });
}