JSFiddle - React, Tailwind, and code Playground

HTML

<script src="http://labs.pegleg.com.au/test_example.json"></script>
<body>
</body>

JavaScript

var width = 960,
    height = 300

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

var force = d3.layout.force()
    .gravity(.05)
    .distance(100)
    .charge(-100)
    .size([width, height]);

d3.json("http://labs.pegleg.com.au/test_example.json", function(error, json) {

    
  /**** Start of bit I'm struggling with ****/
  // make links reference nodes directly for this particular data format:
  var hash_lookup = [];
  // make it so we can lookup nodes in O(1):
  json.Nodes.forEach(function(d, i) {
    hash_lookup[d.Id] = d;
  });
  json.Links.forEach(function(d, i) {
alert(d);
alert(i);
    d.source = hash_lookup[d.Source];
    d.target = hash_lookup[d.Target];
  });
  /**** End of bit I'm struggling with ****/
    
  force
      .nodes(json.Nodes)
      .links(json.Links)
      .start();

  var link = svg.selectAll(".link")
      .data(json.Links)
    .enter().append("line")
      .attr("class", "link");

  var node = svg.selectAll(".node")
      .data(json.Nodes)
    .enter().append("g")
      .attr("class", "node")
      .call(force.drag);

  node.append("circle")
      .attr("class", "node")
      .attr("r", 5);

  node.append("svg:a")
  .attr("xlink:href", function(d){return d.url;}).append("text")
      .attr("dx", 12)
      .attr("dy", ".35em")
      .text(function(d) { return d.name })

  
  force.on("tick", function() {
    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; });

    node.attr("transform", function(d) { return "translate(" + d.x + "," + d.y + ")"; });
  });
});