How d3.voronoi().extent() affects triangles() and links()

See Issue #11 : .triangles() crashing when there is an extent().

Forked from mbostock's block: Delaunay Triangulation

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

.polygon {
   fill: none;
   stroke: #ecc;
}

.links {
  stroke: #413bb3;
  stroke-width: 1.5;
}

.blinks {
  stroke: #c53634;
  stroke-width: 1.5;
}

.triangles {
  fill: #ccf;
}
.btriangles {
  fill: #feeb56;
}

.sites {
  fill: #000;
  stroke: #fff;
}

</style>
<svg width="960" height="400"></svg>
<p>see <a href="https://github.com/d3/d3-voronoi/issues/11">Issue #11</a>.</p>
<p>In blue: without .extent()
  <br>In yellow/red: with .extent()</p>
<script src="https://d3js.org/d3.v4.min.js"></script>
<script src="d3-voronoi.js"></script>
<script>

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

var sites = d3.range(100)
    .map(function(d) { return [ Math.random() * width, Math.random() * height]; });

var voronoi = d3.voronoi();
var bvoronoi = d3.voronoi()
.extent([[1, 1],[width-1, height-1]]);

svg.append("g")
    .attr("class", "polygon")
  .selectAll("path")
  .data(bvoronoi.polygons(sites))
  .enter().append("path")
    .attr("d",  function(d) { return "M" + d.join("L") + "Z"; });

svg.append("g")
    .attr("class", "triangles")
  .selectAll("path")
  .data(voronoi.triangles(sites))
  .enter().append("path")
  .attr("d", function(d) { return "M" + d.join("L") + "Z"; });

svg.append("g")
    .attr("class", "btriangles")
  .selectAll("path")
  .data(bvoronoi.triangles(sites))
  .enter().append("path")
  .attr("d", function(d) { return "M" + d.join("L") + "Z"; });

svg.append("g")
    .attr("class", "links")
  .selectAll("line")
  .data(voronoi.links(sites))
  .enter().append("line")
    .call(redrawLink);

svg.append("g")
    .attr("class", "blinks")
  .selectAll("line")
  .data(bvoronoi.links(sites))
  .enter().append("line")
    .call(redrawLink);

var site = svg.append("g")
    .attr("class", "sites")
  .selectAll("circle")
  .data(sites)
  .enter().append("circle")
    .attr("r", 2.5)
    .call(redrawSite);

function redrawSite(site) {
  site
      .attr("cx", function(d) { return d[0]; })
      .attr("cy", function(d) { return d[1]; });
}

</script>

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