Basic Force Layout

Serves as a basis for other force layout examples.

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

var width = 960, 
    height = 500,
    nodes = [{},{},{}],
    links = [{source: 0, target: 1}, {source: 1, target: 2}, {source: 2, target: 0}];

var force = d3.layout.force()
    .size([width, height])
    .nodes(nodes)
    .links(links)
    .linkDistance(150)
    .on("tick", tick)
    .start();

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

svgLinks = svg.selectAll(".link").data(links)
  .enter().append("line")
    .attr("class", "link");

svgNodes = svg.selectAll(".node").data(nodes)
  .enter().append("circle")
    .attr("class", "node")
    .attr("r", 8)
    .call(force.drag);

function tick() {
  svgNodes
      .attr("cx", function(d) { return d.x })
      .attr("cy", function(d) { return d.y });

svgLinks
      .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 });
};

</script>

Modified http://d3js.org/d3.v3.min.js to a secure url

https://d3js.org/d3.v3.min.js