f_force.js

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

var color = d3.scaleOrdinal(d3.schemeCategory20);

var simulation = d3.forceSimulation()
  .force("link", d3.forceLink())
  .force("charge", d3.forceManyBody())
  .force("center", d3.forceCenter(width / 2, height / 2));

var link = svg.append("g")
  .attr("class", "links")
  .selectAll("line")
  .data(graph.links)
  .enter().append("line")
  .attr("stroke", "black")
  .attr("stroke-width", 1);

var node = svg.append("g")
  .attr("class", "nodes")
  .selectAll("circle")
  .data(graph.nodes)
  .enter().append("circle")
  .attr("r", 4)
  .attr("fill", function (d, i) { return color(d.source); })
  .call(d3.drag()
    .on("start", dragstarted)
    .on("drag", dragged)
    .on("end", dragended));

node.on("mouseover", function (d) {
  var result;
  document.getElementById("nameText").innerHTML = d.name.split(' ')[0];
  // result = graph.links.filter(word => word.source === d.index);
  console.log(graph.links.filter(word => word.source.index === String(d.index)));
  console.log(typeof(String(d.index)));
});

simulation
  .nodes(graph.nodes)
  .on("tick", ticked);

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

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; });
}

function dragstarted(d) {
  if (!d3.event.active) simulation.alphaTarget(0.3).restart();
  d.fx = d.x;
  d.fy = d.y;
}

function dragged(d) {
  d.fx = d3.event.x;
  d.fy = d3.event.y;
}

function dragended(d) {
  if (!d3.event.active) simulation.alphaTarget(0);
  d.fx = null;
  d.fy = null;
}

function returnConnections(i) {

}