JSFiddle - React, Tailwind, and code Playground

HTML

<script src="https://d3js.org/d3.v3.min.js"></script>

CSS

.link {
  fill: url(#gradient);
}

JavaScript

var graph = {
  "nodes":[
    {"name":"Node 1"},
    {"name":"Node 2"}
  ],
  "links":[
    {"source":1,"target":0,"sValue":1, "tValue": 2}
  ]
};


var width = 600,
    height = 400;
    

var color = d3.scale.category20();

var force = d3.layout.force()
    .charge(-120)
    .linkDistance(130)
    .size([width, height]);

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


  force
      .nodes(graph.nodes)
      .links(graph.links)
      .start();
      
var gradient = d3.select("svg").append("defs")
    .append("linearGradient")
    .attr("id", "gradient")
    .attr("spreadMethod", "pad");
  //start color white
  gradient.append("stop")
    .attr("offset", "0%")
    .attr("stop-color", "red")
    .attr("stop-opacity", 1);
  //end color steel blue
	gradient.append("stop")
    .attr("offset", "100%")
    .attr("stop-color", "green")
    .attr("stop-opacity", 1);

  var link = svg.selectAll("path.link")
    .data(graph.links)
    .enter().append("svg:path")
    .attr("class", "link")
    .style("stroke-width", function(d) { return Math.sqrt(d.value); })
    .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; });

  var node = svg.selectAll(".node")
      .data(graph.nodes)
      .enter().append("circle")
      .attr("class", "node")
      .attr("r", 20)
      .style("fill", function(d) { return color(d.group); })
      .call(force.drag);

  node.append("title")
      .text(function(d) { return d.name; });

  force.on("tick", function() {
     d3.selectAll(".link")
            .attr("d", function (d) {
                 
                    var radius = 10;
                    
                    var linkVector = new Vector2(d.target.x-d.source.x,d.target.y-d.source.y).getUnitVector();
                    var perpVector =...