d3v4 JSON Tree

This is a response to the stackoverflow.com question How do I create a tree layout using JSON data in d3.v4 - without stratify().

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

.node circle {
  fill: #999;
}

.node text {
  font: 10px sans-serif;
}

.node--internal circle {
  fill: #555;
}

.node--internal text {
  text-shadow: 0 1px 0 #fff, 0 -1px 0 #fff, 1px 0 0 #fff, -1px 0 0 #fff;
}

.link {
  fill: none;
  stroke: #555;
  stroke-opacity: 0.4;
  stroke-width: 1.5px;
}

</style>
<svg width="500" height="300"></svg>
<script src="//d3js.org/d3.v4.min.js"></script>
<script>

var svg = d3.select("svg"),
    width = +svg.attr("width"),
    height = +svg.attr("height"),
    g = svg.append("g").attr("transform", "translate(60,0)");

var tree = d3.cluster()
    .size([height, width - 160]);

var stratify = d3.stratify()
    .parentId(function(d) { return d.id.substring(0, d.id.lastIndexOf(".")); });

d3.json("treeData.json", function(error, treeData) {
  if (error) throw error;

var root = d3.hierarchy(treeData);
  tree(root);

var link = g.selectAll(".link")
      .data(root.descendants().slice(1))
    .enter().append("path")
      .attr("class", "link")
      .attr("d", function(d) {
        return "M" + d.y + "," + d.x
            + "C" + (d.parent.y + 100) + "," + d.x
            + " " + (d.parent.y + 100) + "," + d.parent.x
            + " " + d.parent.y + "," + d.parent.x;
      });

var node = g.selectAll(".node")
      .data(root.descendants())
    .enter().append("g")
      .attr("class", function(d) { return "node" + (d.children ? " node--internal" : " node--leaf"); })
      .attr("transform", function(d) { 
        return "translate(" + d.y + "," + d.x + ")"; 
      })

node.append("circle")
      .attr("r", 2.5);

node.append("text")
      .attr("dy", 3)
      .attr("x", function(d) { return d.children ? -8 : 8; })
      .style("text-anchor", function(d) { return d.children ? "end" : "start"; })
      .text(function(d) { 
        return d.data.name;
      });
});

</script>

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