TopoJSON Layers

Adding a little animation to the U.S. TopoJSON example to illustrate the different layers.

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

svg {
  position: absolute;
  top: 0;
  left: 0;
}

path {
  stroke-linejoin: round;
}

.land-glow use {
  fill-opacity: .2;
  filter: url(#blur);
}

.land-fill {
  fill: #fff;
}

.state-boundary {
  fill: none;
  stroke: #777;
  stroke-width: .70px;
}

.county-boundary {
  fill: none;
}

.land-fill,
.county-boundary {
  stroke: #777;
  stroke-width: .35px;
}

</style>
<body>
<script src="//d3js.org/d3.v3.min.js"></script>
<script src="//d3js.org/topojson.v1.min.js"></script>
<script>

var width = 960,
    height = 600;

var projection = d3.geo.albersUsa()
    .scale(1285)
    .translate([width / 2, height / 2]);

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

d3.json("/../../data/us.json", function(error, us) {
  if (error) throw error;

var svgGlow = d3.select("body").append("svg")
      .attr("width", width)
      .attr("height", height)
      .attr("class", "land-glow");

svgGlow.append("defs").append("path")
      .datum(topojson.feature(us, us.objects.land))
      .attr("id", "land")
      .attr("d", path);

svgGlow.append("filter")
      .attr("id", "blur")
    .append("feGaussianBlur")
      .attr("stdDeviation", 5);

svgGlow.append("use")
      .attr("xlink:href", "#land");

d3.select("body").append("svg")
      .attr("width", width)
      .attr("height", height)
      .attr("class", "land-fill")
    .append("use")
      .attr("xlink:href", "#land");

d3.select("body").append("svg")
      .attr("width", width)
      .attr("height", height)
      .attr("class", "county-boundary")
    .append("path")
      .datum(topojson.mesh(us, us.objects.counties, function(a, b) {
        return a !== b // a border between two counties
            && (a.id === 53000 || b.id === 5300 // where a and b are in puget sound
              || a.id % 1000 && b.id % 1000) // or a and b are not in a lake
            && !(a.id / 1000 ^ b.id / 1000); // and a and b are in the same state
      }))
      .attr("d", path);

d3.select("body").append("svg")
      .attr("width", width)
      .attr("height", height)
      .attr("class", "state-boundary")
    .append("path")
      .datum(topojson.mesh(us, us.objects.states, function(a, b) {
        return a !== b; // a border between two states
      }))
      .attr("d", path);

var svg = d3.selectAll("svg").style("opacity", 0);
  animation();

function animation() {
    var duration = 750,
        delay = 750,
        n = svg[0].length;

svg.transition()
        .duration(duration)
        .delay(function(d, i) { return (duration + delay) * (n - 1 - i); })
        .style("opacity", 1)
      .transition()
        .delay(function(d, i) { return (duration + delay) * (n + i); })
        .style("opacity", 0)
        .each("end", function(d, i) { if (i === n - 1) animation(); });
  }
});

d3.select(self.frameElement).style("height", height + "px");

</script>

Changed /mbostock/raw/4090846/us.json to a local referenece

https://d3js.org/d3.v3.min.js

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