D3v4 Responsive Map

D3 Map that is responsive to screen size on load

<!DOCTYPE html>
<head>
  <meta charset="utf-8">
  <script src="https://d3js.org/d3.v4.js"></script>
  
  <script src="https://unpkg.com/topojson-client@3"></script>
  <style>
    body { margin:10px;position:fixed;top:0;right:0;bottom:0;left:0; }
    #map { border:1px solid #000; }
  </style>
</head>

<body>
  <div id="map"></div>
  <script>
    var map = d3.select("#map");
    var width = map.node().getBoundingClientRect().width;
    var height = width / 2;
    
    var svg = map.append("svg")
    .attr("width", width)
    .attr("height", height);
    
    var projection = d3.geoMercator();
    
    var path = d3.geoPath().projection(projection);
      
d3.json("https://unpkg.com/world-atlas@1/world/110m.json", function(error, world) {
  if (error) throw error;

svg.selectAll("path")
       .data(topojson.feature(world, world.objects.countries).features)
       .enter().append("path")
       .attr("d", path);
  
});
 
  </script>
</body>

https://d3js.org/d3.v4.js

https://d3js.org/topojson.v2.min.js

https://unpkg.com/topojson-client@3