使用d3js向地图添加标注

var svg = d3.select("body")
            .append("svg")
            .attr("width", width)
            .attr("height", height);

var path = d3.geoPath()
             .projection(projection);

svg.selectAll("path")
   .data(mapData.features)
   .enter()
   .append("path")
   .attr("d", path)
   .attr("fill", "gray")
   .attr("stroke", "white");

var markers = [
  { name: "Marker 1", coordinates: [longitude1, latitude1] },
  { name: "Marker 2", coordinates: [longitude2, latitude2] },
  // ...
];

svg.selectAll("circle")
   .data(markers)
   .enter()
   .append("circle")
   .attr("cx", function(d) { return projection(d.coordinates)[0]; })
   .attr("cy", function(d) { return projection(d.coordinates)[1]; })
   .attr("r", 5)
   .attr("fill", "red");