echarts地图map城市间如何连线

let bjdata = [
    [{name:'北京'}, {name:'上海',value:95}],
    [{name:'北京'}, {name:'广州',value:90}]
];

let convert = (data) => {
    let res = [];
    for (var i = 0; i < data.length; i++) {
        var dataitem = data[i];
        var from = geocoordmap[dataitem[0].name];
        var to = geocoordmap[dataitem[1].name];
        if (fromcoord && tocoord) {
            res.push({
                fromname: dataitem[0].name,
                toname: dataitem[1].name,
                coords: [from, to]
            });
        }
    }

    return res;
};


series: [

{
    name: '北京',
    type: 'lines',
    zlevel: 1,
    symbol: ['none'],
    symbolsize: 10,
    linestyle: {
        normal: {
            color: '#f00',
            width: 1,
            opacity: 0.6,
            curveness: 0.2
        }
    },
    data: convert(bjdata)
}

]