D3v4 Map with Zoom Constraints

D3 Map that is responsive to screen size on load

forked from piwodlaiwo's block: D3v4 Responsive Map

<!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>
    const map = d3.select("#map");
    const width = map.node().getBoundingClientRect().width;
    const height = width / 2;

const projection = d3.geoMercator(); 
    const path = d3.geoPath().projection(projection);
    
    const zoom = d3.zoom()
    .scaleExtent([1, 40])
    .translateExtent([[0,0], [width, height]])
    .extent([[0, 0], [width, height]])
    .on("zoom", zoomed);
    
    const svg = map.append("svg")
    .attr("width", width)
    .attr("height", height)
    .call(zoom);
    
    const g = svg.append("g");

d3.json("https://unpkg.com/world-atlas@1/world/110m.json", function(error, world) {
  if (error) throw error;

g.selectAll("path")
       .data(topojson.feature(world, world.objects.countries).features)
       .enter().append("path")
       .attr("d", path);
  
});
    
function zoomed(){
  g.attr("transform", d3.event.transform);
}   
  </script>
</body>

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

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

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