d3.js tree from csv

This is a simple d3.js tree diagram put together in response to a question on Stack Overflow

It is aimed at providing some exposure to some d3.js functions and should be taken in context with the text of the book which can be downloaded for free from Leanpub.

<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="utf-8">

<title>Collapsible Tree Example</title>

<style>

.node circle {
	  fill: #fff;
	  stroke: steelblue;
	  stroke-width: 3px;
	}

.node text { font: 12px sans-serif; }

.link {
	  fill: none;
	  stroke: #ccc;
	  stroke-width: 2px;
	}
	
    </style>

</head>

<body>

<script src="https://cdnjs.cloudflare.com/ajax/libs/d3/3.5.17/d3.min.js"></script>
	
<script>

// ************** Generate the tree diagram	 *****************
var margin = {top: 20, right: 120, bottom: 20, left: 120},
	width = 960 - margin.right - margin.left,
	height = 500 - margin.top - margin.bottom;
	
var i = 0;

var tree = d3.layout.tree()
	.size([height, width]);

var diagonal = d3.svg.diagonal()
	.projection(function(d) { return [d.y, d.x]; });

var svg = d3.select("body").append("svg")
	.attr("width", width + margin.right + margin.left)
	.attr("height", height + margin.top + margin.bottom)
  .append("g")
	.attr("transform", "translate(" + margin.left + "," + margin.top + ")");

// load the external data
d3.csv("treedata.csv", function(error, data) {

// *********** Convert flat data into a nice tree ***************
// create a name: node map
var dataMap = data.reduce(function(map, node) {
	map[node.name] = node;
	return map;
}, {});

// create the tree array
var treeData = [];
data.forEach(function(node) {
	// add to parent
	var parent = dataMap[node.parent];
	if (parent) {
		// create child array if it doesn't exist
		(parent.children || (parent.children = []))
			// add node to child array
			.push(node);
	} else {
		// parent is null or missing
		treeData.push(node);
	}
});

root = treeData[0];
  update(root);
});

function update(source) {

// Compute the new tree layout.
  var nodes = tree.nodes(root).reverse(),
	  links = tree.links(nodes);

// Normalize for fixed-depth.
  nodes.forEach(function(d) { d.y = d.depth * 180; });

// Declare the nodesâ€¦
  var node = svg.selectAll("g.node")
	  .data(nodes, function(d) { return d.id || (d.id = ++i); });

// Enter the nodes.
  var nodeEnter = node.enter().append("g")
	  .attr("class", "node")
	  .attr("transform", function(d) { 
		  return "translate(" + d.y + "," + d.x + ")"; });

nodeEnter.append("circle")
	  .attr("r", 10)
	  .style("fill", "#fff");

nodeEnter.append("text")
	  .attr("x", function(d) { 
		  return d.children || d._children ? -13 : 13; })
	  .attr("dy", ".35em")
	  .attr("text-anchor", function(d) { 
		  return d.children || d._children ? "end" : "start"; })
	  .text(function(d) { return d.name; })
	  .style("fill-opacity", 1);

// Declare the linksâ€¦
  var link = svg.selectAll("path.link")
	  .data(links, function(d) { return d.target.id; });

// Enter the links.
  link.enter().insert("path", "g")
	  .attr("class", "link")
	  .attr("d", diagonal);

}

</script>
	
  </body>
</html>

https://cdnjs.cloudflare.com/ajax/libs/d3/3.5.17/d3.min.js