Force Layout with Voronoi Cells and Add/Remove Node functionality

Created out of a SO question on force directed graphs with voronoi.

The layout includes:

Charged force layout,
Voronoi click based click events for dragging/removing, and
Dynamic adding/removing of nodes.

The voronoi updates with the force layout, based on:

Mike's circle dragging block

and

Mike's force directed lyaout block

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

.cell {
  pointer-events: all;
  fill: none;
  stroke: #666;
  stroke-opacity: 0.2;
}

.active circle {
  stroke: #000;
  stroke-width: 2px;
}

</style>
<div id="control"> </div>
<svg width="960" height="500"></svg>
<script src="https://d3js.org/d3.v4.min.js"></script>
<script>

var svg = d3.select("svg"),
    width = +svg.attr("width"),
    height = +svg.attr("height"),
    radius = 32;

var n = 0;
var circles = d3.range(15).map(function() {
  return {
	n: n++,
    x: Math.round(Math.random() * (width - radius * 2) + radius),
    y: Math.round(Math.random() * (height - radius * 2) + radius)
  };
});

// control add/remove
var addNew = false;
d3.select('#control').append('input')
	.attr('type','button')
	.attr('value', addNew ? "Add" : "Remove")
	.on('click', function(d) {
		addNew = !addNew;
		d3.select(this).attr('value', addNew ? "Add" : "Remove")
		d3.selectAll('g').on('click', (addNew) ? add : remove);
	});

var color = d3.scaleOrdinal()
    .range(d3.schemeCategory20);

var voronoi = d3.voronoi()
    .x(function(d) { return d.x; })
    .y(function(d) { return d.y; })
    .extent([[-1, -1], [width + 1, height + 1]]);

var circle = svg.selectAll("g")
  .data(circles)
  .enter().append("g")
  .attr('id',function(d) { return 'g-'+d.n })
  .call(d3.drag()
        .on("start", dragstarted)
        .on("drag", dragged)
        .on("end", dragended))
  .on('click', (addNew) ? add : remove);

var cell = circle.append("path")
  .data(voronoi.polygons(circles))
    .attr("d", renderCell)
	.attr("class","cell")
    .attr("id", function(d) {  return "cell-" + d.data.n; });

circle.append("clipPath")
    .attr("id", function(d) { return "clip-" + d.n; })
  .append("use")
    .attr("xlink:href", function(d) { return "#cell-" + d.n; });

circle.append("circle")
    .attr("clip-path", function(d) { return "url(#clip-" + d.n + ")"; })
    .attr("cx", function(d) { return d.x; })
    .attr("cy", function(d) { return d.y; })
    .attr("r", radius)
    .style("fill", function(d) { return color(d.n); });
	
circle.append("text")
    .attr("clip-path", function(d, i) { return "url(#clip-" + i + ")"; })
    .attr("x", function(d) { return d.x; })
    .attr("y", function(d) { return d.y; })
    .attr("dy", '0.35em')
    .attr("text-anchor", function(d) { return 'middle'; })
    .attr("opacity", 0.6)
    .style("font-size", "1.8em")
    .style("font-family", "Sans-Serif")
    .text(function(d) { return d.n; })
	
var simulation = d3.forceSimulation()
   .nodes(circles)
   .force('charge', d3.forceManyBody());

simulation.nodes(circles)
 .on('tick',ticked);
 
     
function ticked() {
circle.selectAll('circle')
  .attr("cx", function(d) { return d.x; })
  .attr("cy", function(d) { return d.y; })
  
circle.selectAll('text')
  .attr("x", function(d) { return d.x; })
  .attr("y", function(d) { return d.y; });

cell = cell.data(voronoi.polygons(circles)).attr("d", renderCell);

}

function dragstarted(d) {
  if (!d3.event.active) simulation.alphaTarget(0.3).restart();
	d.fx = d.x;
	d.fy = d.y;
}

function dragged(d) {
  d3.select(this).select("circle").attr("cx", d.x = d3.event.x).attr("cy", d.y = d3.event.y);
  cell = cell.data(voronoi.polygons(circles)).attr("d", renderCell);
  d.fx = d3.event.x;
  d.fy = d3.event.y;
  
  
}

function dragended(d) {
 if (!d3.event.active) simulation.alphaTarget(0);
  d.fx = null;
  d.fy = null;
}

function remove () {

d3.select(this).raise(); 
	var id = d3.select(this).attr('id').split('-')[1];
	id = +id;
	
	// Get the clicked item:
	var index = circles.map(function(d) {
		return d.n;
	}).indexOf(id);
	
	circles.splice(index,1);
	
	// Update circle data:
	var circle = svg.selectAll("g")
	  .data(circles);
	  
	circle.exit().remove();
	circle.selectAll("clipPath").exit().remove();
	circle.selectAll("circle").exit().remove();
	circle.selectAll("text").exit().remove();

//// Update voronoi:
	d3.selectAll('.cell').remove();
	cell = circle.append("path")
	  .data(voronoi.polygons(circles))
	  .attr("d", renderCell)
	  .attr("class","cell")
	  .attr("id", function(d) {  return "cell-" + d.data.n; });
	
	simulation.nodes(circles)
		.on('tick',ticked);
}

cell = circle.selectAll("path")
		.data(voronoi.polygons(circles)).enter();
		
	cell.select('#g-'+newIndex).append('path')
	  .attr("d", renderCell)
	  .attr("class","cell")
	  .attr("id", function(d) { console.log(d.data); return "cell-" + d.data.n; });

newCircle.data(circles).enter();
	
	newCircle.append("clipPath")
		.attr("id", function(d) { return "clip-" + d.n; })
	    .append("use")
		.attr("xlink:href", function(d) { return "#cell-" + d.n; });

newCircle.append("circle")
		.attr("clip-path", function(d) { return "url(#clip-" + d.n + ")"; })
		.attr("cx", function(d) { return d.x; })
		.attr("cy", function(d) { return d.y; })
		.attr("r", radius)
		.style("fill", function(d) { return color(d.n); });
		
	newCircle.append("text")
      .attr("clip-path", function(d) { return "url(#clip-" + d.n + ")"; })
      .attr("x", function(d) { return d.x; })
      .attr("y", function(d) { return d.y; })
      .attr("dy", '0.35em')
      .attr("text-anchor", function(d) { return 'middle'; })
      .attr("opacity", 0.6)
      .style("font-size", "1.8em")
      .style("font-family", "Sans-Serif")
      .text(function(d) { return d.n; })
	  
	cell = d3.selectAll('.cell');
		
	d3.select("#cell-"+newIndex).lower(); // ensure the path is above the circle in svg.
		
	simulation.nodes(circles)
	  .on('tick',ticked);

}

function renderCell(d) {
  return d == null ? null : "M" + d.join("L") + "Z";
}

</script>

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