chart.js 显示点数值

var ctx = document.getElementById('myChart').getContext('2d');
var myChart = new Chart(ctx, {
    type: 'line',
    data: {
        labels: ['January', 'February', 'March', 'April', 'May', 'June', 'July'],
        datasets: [{
            label: 'My First dataset',
            backgroundColor: 'rgb(255, 99, 132)',
            borderColor: 'rgb(255, 99, 132)',
            data: [0, 10, 5, 2, 20, 30, 45],
            pointRadius: 5,
            pointHoverRadius: 7,
            pointBackgroundColor: 'rgb(255, 99, 132)',
            pointHoverBackgroundColor: 'rgb(220,220,220)'
        }]
    },
    options: {
        plugins: {
            tooltip: {
                enabled: false // 禁用默认的tooltip
            },
            datalabels: {
                color: '#fff',
                anchor: 'end',
                align: 'top',
                formatter: function(value, context) {
                    return value;
                }
            }
        },
        scales: {
            y: {
                beginAtZero: true
            }
        }
    }
});