D3v4 Collapsible Force Layout

Click to expand or collapse nodes in the tree. Built with D3. Collapsible Force Layout

<!DOCTYPE html>
<meta charset="utf-8">
<title>Force-Directed Graph</title>
<style>

.node {
  cursor: pointer;
  stroke: #3182bd;
  stroke-width: 1.5px;
}

.link {
  fill: none;
  stroke: #9ecae1;
  stroke-width: 1.5px;
}

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

var width = 960,
    height = 500,
    root;

var force = d3.layout.force()
    .size([width, height])
    .on("tick", tick);

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

var link = svg.selectAll(".link"),
    node = svg.selectAll(".node");

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

root = json;
  update();
});

function update() {
  var nodes = flatten(root),
      links = d3.layout.tree().links(nodes);

// Restart the force layout.
  force
      .nodes(nodes)
      .links(links)
      .start();

// Update the links…
  link = link.data(links, function(d) { return d.target.id; });

// Exit any old links.
  link.exit().remove();

// Enter any new links.
  link.enter().insert("line", ".node")
      .attr("class", "link")
      .attr("x1", function(d) { return d.source.x; })
      .attr("y1", function(d) { return d.source.y; })
      .attr("x2", function(d) { return d.target.x; })
      .attr("y2", function(d) { return d.target.y; });

// Update the nodes…
  node = node.data(nodes, function(d) { return d.id; }).style("fill", color);

// Exit any old nodes.
  node.exit().remove();

// Enter any new nodes.
  node.enter().append("circle")
      .attr("class", "node")
      .attr("cx", function(d) { return d.x; })
      .attr("cy", function(d) { return d.y; })
      .attr("r", function(d) { return Math.sqrt(d.size) / 10 || 4.5; })
      .style("fill", color)
      .on("click", click)
      .call(force.drag);
}

node.attr("cx", function(d) { return d.x; })
      .attr("cy", function(d) { return d.y; });
}

// Color leaf nodes orange, and packages white or blue.
function color(d) {
  return d._children ? "#3182bd" : d.children ? "#c6dbef" : "#fd8d3c";
}

// Toggle children on click.
function click(d) {
  if (!d3.event.defaultPrevented) {
    if (d.children) {
      d._children = d.children;
      d.children = null;
    } else {
      d.children = d._children;
      d._children = null;
    }
    update();
  }
}

// Returns a list of all nodes under the root.
function flatten(root) {
  var nodes = [], i = 0;

function recurse(node) {
    if (node.children) node.children.forEach(recurse);
    if (!node.id) node.id = ++i;
    nodes.push(node);
  }

recurse(root);
  return nodes;
}

</script>

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