JSFiddle - React, Tailwind, and code Playground

HTML

<!DOCTYPE html>
<html>
  <head>
    <title>Force-Directed Layout</title>
    <script type="text/javascript" src="http://mbostock.github.com/d3/d3.js"></script>
    <script type="text/javascript" src="http://mbostock.github.com/d3/d3.geom.js"></script>
    <script type="text/javascript" src="http://mbostock.github.com/d3/d3.layout.js"></script>
  </head>
  <body>
  </body>
</html>

CSS

circle {
  stroke-width: 1.5px;
}

line {
  stroke: #999;
}

JavaScript

var w = 960,
    h = 500,
    r = 6,
    fill = d3.scale.category20();

var force = d3.layout.force().gravity(.01).charge(-120).linkDistance(30).size([w, h]);

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

d3.json("http://bl.ocks.org/d/1129492/readme.json", function(json) {
    var link = svg.selectAll("line").data(json.links).enter().append("svg:line");

    var node = svg.selectAll("circle").data(json.nodes).enter().append("svg:circle").attr("r", r - .75).style("fill", function(d) {
        return fill(d.group);
    }).style("stroke", function(d) {
        return d3.rgb(fill(d.group)).darker();
    }).call(force.drag).on("mouseover", fade(.1)).on("mouseout", fade(1));;

    force.nodes(json.nodes).links(json.links).on("tick", tick).start();

    function tick() {
        node.attr("cx", function(d) {
            return d.x = Math.max(r, Math.min(w - r, d.x));
        }).attr("cy", function(d) {
            return d.y = Math.max(r, Math.min(h - r, d.y));
        });

        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;
        });
    }

    function fade(opacity) {
        return function(d, i) {
            //fade all elements
            svg.selectAll("circle, line").style("opacity", opacity);

            var associated_links = svg.selectAll("line").filter(function(d) {
                return d.source.index == i || d.target.index == i;
            }).each(function(dLink, iLink) {
                //unfade links and nodes connected to the current node
                d3.select(this).style("opacity", 1);
                //THE FOLLOWING CAUSES: Uncaught TypeError: Cannot call method 'setProperty' of undefined
                d3.select(dLink.source).style("opacity", 1);
               ...