drag = simulation => {
  
    function dragstarted(event) {
      if (!event.active) simulation.alphaTarget(0.3).restart();
      event.subject.fx = event.subject.x;
      event.subject.fy = event.subject.y;
    }
    
    function dragged(event) {
      event.subject.fx = event.x;
      event.subject.fy = event.y;
    }
    
    function dragended(event) {
      if (!event.active) simulation.alphaTarget(0);
      event.subject.fx = null;
      event.subject.fy = null;
    }
    
    return d3.drag()
        .on("start", dragstarted)
        .on("drag", dragged)
        .on("end", dragended);
  }

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

var simulation = d3.forceSimulation()
    .force("charge", d3.forceManyBody().strength(-200))
    .force("link", d3.forceLink().id(function(d) { return d.id; }).distance(40))
    .force("x", d3.forceX(width / 2))
    .force("y", d3.forceY(height / 2))
    .on("tick", ticked);

var link = svg.selectAll(".link"),
    node = svg.selectAll(".node");

graph = {{data}}


simulation.nodes(graph.nodes);
simulation.force("link").links(graph.links);

link = link
.data(graph.links)
.enter().append("line")
    .attr("class", "link");

node = node
.data(graph.nodes)
.enter().append("circle")
    .attr("class", "node")
    .attr("r", 6)
    .style("fill", function(d) { return d.id; });


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