D3 Examples - Zoomable world map with highlighted locations

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<!DOCTYPE html>
<meta charset="utf-8">
<style>
​
.background {
  fill: none;
  pointer-events: all;
}
​
#country {
  fill: #aaa;
}
​
#country-borders {
  fill: none;
  stroke: #fff;
  stroke-width: 1.5px;
  stroke-linejoin: round;
  stroke-linecap: round;
  pointer-events: none;
}
​
</style>
<body>
<script src="https://d3js.org/d3.v3.min.js"></script>
<script src="https://d3js.org/topojson.v1.min.js"></script>
<script>
​
var width = 960,
    height = 500;
​
var projection = d3.geo.mercator()
    .scale(100)
    .translate([width / 2, height / 2]);
​
var path = d3.geo.path()
    .projection(projection);
​
var zoom = d3.behavior.zoom()
    .translate(projection.translate())
    .scale(projection.scale())
    .scaleExtent([100, 1000])
    .on("zoom", zoomed);
​
var svg = d3.select("body").append("svg")
    .attr("width", width)
    .attr("height", height);
​
var g = svg.append("g")
    .call(zoom);
​
var dotSpot = [[20,20], [10,10]];
​
console.log(projection(dotSpot[0])[0])
​
g.append("rect")
    .attr("class", "background")
    .attr("width", width)
    .attr("height", height);
​
d3.json("world.json", function(error, nations) {
​
  console.log(nations)
  g.append("g")
      .attr("id", "country")
    .selectAll("path")
      .data(topojson.feature(nations, nations.objects.countries).features)
    .enter().append("path")
      .attr("d", path);
​
  g.append("path")
      .datum(topojson.mesh(nations, nations.objects.countries, function(a, b) { return a !== b; }))
      .attr("id", "country-borders")
      .attr("d", path);
​
  g.selectAll("circle")
        .data(dotSpot).enter()
      .append("circle")
        .attr("cx", function (d,i) { return projection(d)[0]; })
        .attr("cy", function (d,i) { return projection(d)[1]; })
        .attr("r", "10px")
        .style("fill", "red");
});
​
function zoomed() {
  projection.translate(d3.event.translate).scale(d3.event.scale);
  g.selectAll("path").attr("d", path)
  g.selectAll("circle")
    .attr("cx", function (d,i) { return projection(d)[0]; })
    .attr("cy", function (d,i) { return projection(d)[1]; })
    .attr("r", "10px")
    .style("fill", "red");
}
​
</script>
    