虽然我还不明白为什么：

series:           ...
    data:         ...
        csvURL:   ...

......不起作用，以下方法将起作用：

(async () => {

    const topology = await fetch(
        'https://code.highcharts.com/mapdata/countries/us/us-all.topo.json'
    ).then(response => response.json());

    // Instantiate the map
    Highcharts.mapChart('container', {

        chart: {
            map: topology,
            borderWidth: 1
        },

        data: {
            //csv: document.getElementById('csv').innerHTML,
            csvURL: 'http://localhost/testData.csv',
            seriesMapping: [{
                code: 0,
                value: 1,
                label: 2
            }]
        },

        title: {
            text: 'US population density (/km²)'
        },

        exporting: {
            sourceWidth: 600,
            sourceHeight: 500
        },

        legend: {
            layout: 'horizontal',
            borderWidth: 0,
            backgroundColor: 'rgba(255,255,255,0.85)',
            floating: true,
            verticalAlign: 'top',
            y: 25
        },

        mapNavigation: {
            enabled: true
        },

        colorAxis: {
            min: 1,
            type: 'logarithmic',
            minColor: '#EEEEFF',
            maxColor: '#000022',
            stops: [
                [0, '#EFEFFF'],
                [0.67, '#4444FF'],
                [1, '#000022']
            ]
        },

        plotOptions: {
            series: {
                animation: {
                    duration: 1000
                },
                joinBy: ['postal-code', 'code'],
                dataLabels: {
                    enabled: true,
                    color: '#FFFFFF',
                    format: '{point.code}'
                },
                name: 'Population density',
                tooltip: {
                    pointFormat: '{point.code}: {point.value}/km²'
                }
            }
        }
    });

})();

虽然我还是很想知道为什么它在我最初的问题中不起作用。