pack forever by enjalot

index.html

<!DOCTYPE html>
<html>
<head>
<style>
  body {
    text-align: center;
    background-color: #111;
  }
  button {
    font-size: 24px;
  }
</style>
</head>
<body>

<div></div>
<script src="https://d3js.org/d3.v4.min.js"></script>
<script>

var diameter = 250,
    circleSize = d3.scaleLinear().range([100, 5000000]);

  var duration = 300;
  
var svg = d3.select("div")
  .append("svg")
  .attr("width", diameter * 2)
  .attr("height", diameter * 2)
  .append("g")
    .attr("transform", "translate(" + diameter / 2 + " " + diameter / 2 + ")");

var children = initialLayout(randomData(40));

var radiusScale = d3
  .scaleSqrt()
  .domain([children[0].value, children[1].value])
  .range([children[0].r, children[1].r]);



render();

setInterval(function() {
  addCircle()
  render();
}, duration - 5)
  
function render() {
  var circles = svg
    .selectAll("circle")
    .data(children, function(d) {
      return +d.id;
    })
    .style("fill", "#66bbdd");

  var entering = circles
    .enter()
    .append("circle")
    .style("fill", "yellow")
    .style("stroke", "black")
    .attr("r", 0)
    .attr("cx", d => d.x)
    .attr("cy", d => d.y);

  circles
    .merge(entering)
    .transition()
    .duration(duration)
    .attr("cx", d => d.x)
    .attr("cy", d => d.y)
    .attr("r", d => d.r);
}

function addCircle() {

  var newValue = circleSize(Math.random()),
    neighbor = d3.scan(children, function(a, b) {
      return Math.abs(a.value - newValue) - Math.abs(b.value - newValue)
    }),
    newNode = {
      r: radiusScale(newValue),
      id: children.length + 1,
      x: children[neighbor].x,
      y: children[neighbor].y,
    },
    links = [{
      distance: newNode.r + children[neighbor].r,
      source: children.length,
      target: neighbor
    }];

  children.push(newNode);

  children.forEach(function(d) {
    d.x0 = d.x;
    d.y0 = d.y;
  });

  var simulation = d3
    .forceSimulation(children)
    .force("cx", d3.forceX().x(d => diameter / 2).strength(0.02))
    .force("cy", d3.forceY().y(d => diameter / 2).strength(0.02))
    .force("link", d3.forceLink(links).distance(d => d.distance).strength(0.5))
    .force("x", d3.forceX().x(d => d.x0).strength(0.1))
    .force("y", d3.forceY().y(d => d.y0).strength(0.1))
    .force("collide", d3.forceCollide().strength(0.8).radius(d => d.r + 1))
    .stop();

  while (simulation.alpha() > 0.001) {
    simulation.tick();
  }
}

function initialLayout(data) {
  var stratify = d3
    .stratify()
    .id(d => d.id)
    .parentId(d => d.parent);

  var pack = d3.pack().size([diameter - 4, diameter - 4]);

  var root = stratify(data)
    .sum(d => d.size)
    .sort((a, b) => b.value - a.value);

  return pack(root).leaves();
}

function randomData(numNodes) {
  return d3.range(numNodes).map(function(d) {
    return {
      id: d,
      name: d ? "Leaf" : "Root",
      size: circleSize(Math.random()),
      parent: d ? 0 : undefined
    };
  });
}

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