Zoom to Bounding Box II d3v4

A variant of the Zoom to Bounding Box example that uses zoom transitions to smoothly interpolate between different views. This example also allows you to freely pan and zoom with the mouse (or touch).

forked from mbostock's block: Zoom to Bounding Box II

<!DOCTYPE html>
<meta charset="utf-8">
<style>

.background {
  fill: none;
  pointer-events: all; 
}

.feature {
  fill: #ccc;
  cursor: pointer;
}

.feature.active {
  fill: red;
}

.mesh {
  fill: none;
  stroke: #fff;
  stroke-linecap: round;
  stroke-linejoin: round;
}

</style>
<body>
<script src="//d3js.org/d3.v4.min.js"></script>
<script src="//d3js.org/topojson.v1.min.js"></script>
<script>

var width = 960,
    height = 500,
    active = d3.select(null);

var projection = d3.geoAlbersUsa()
    .scale(1000)
    .translate([width / 2, height / 2]);
 
var zoom = d3.zoom()
    .on("zoom", zoomed);
  
var initialTransform = d3.zoomIdentity
    .translate(0,0)
    .scale(1);
  
var path = d3.geoPath()
    .projection(projection);

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

svg.append("rect")
    .attr("class", "background")
    .attr("width", width)
    .attr("height", height)
    .on("click", reset);

var g = svg.append("g");

svg
    .call(zoom) // delete this line to disable free zooming
    .call(zoom.transform, initialTransform);

d3.json("https://gist.githubusercontent.com/mbostock/4090846/raw/d534aba169207548a8a3d670c9c2cc719ff05c47/us.json", function(error, us) {
  if (error) throw error;

g.selectAll("path")
      .data(topojson.feature(us, us.objects.states).features)
    .enter().append("path")
      .attr("d", path)
      .attr("class", "feature")
      .on("click", clicked);

g.append("path")
      .datum(topojson.mesh(us, us.objects.states, function(a, b) { return a !== b; }))
      .attr("class", "mesh")
      .attr("d", path);
});

function clicked(d) {
  if (active.node() === this) return reset();
  active.classed("active", false);
  active = d3.select(this).classed("active", true);

var bounds = path.bounds(d),
      dx = bounds[1][0] - bounds[0][0],
      dy = bounds[1][1] - bounds[0][1],
      x = (bounds[0][0] + bounds[1][0]) / 2,
      y = (bounds[0][1] + bounds[1][1]) / 2,
      scale = Math.max(1, Math.min(8, 0.9 / Math.max(dx / width, dy / height))),
      translate = [width / 2 - scale * x, height / 2 - scale * y];

var transform = d3.zoomIdentity
    .translate(translate[0], translate[1])
    .scale(scale);

svg.transition()
      .duration(750)
      .call(zoom.transform, transform);
}

function reset() {
  active.classed("active", false);
  active = d3.select(null);

svg.transition()
      .duration(750)
      .call(zoom.transform, initialTransform);
}

function zoomed() {
  var transform = d3.event.transform;

g.style("stroke-width", 1.5 / transform.k + "px");
  g.attr("transform", transform);
}

// If the drag behavior prevents the default click,
// also stop propagation so we don’t click-to-zoom.
function stopped() {
  if (d3.event.defaultPrevented) d3.event.stopPropagation();
}

</script>

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

https://d3js.org/topojson.v1.min.js