Sankey with circular link and animated dashes

A version of the Sankey chart with circular links, with a stroke-dasharray animated to show direction.

The relevant piece of code:

    arrowsG.selectAll("path")
      .style("stroke-width", "10")
      .style("stroke-dasharray", "10,10")

    let duration = 5
    let maxOffset = 10;
    let percentageOffset = 1;

    var animateDash = setInterval(updateDash, duration);

    function updateDash() {

      arrowsG.selectAll("path")
      .style("stroke-dashoffset", percentageOffset * maxOffset)

      percentageOffset = percentageOffset == 0 ? 1 : percentageOffset - 0.01

    }
    ```

<!DOCTYPE html>
<html>

<head>

<title>Sankey with circular links</title>
  <style>
    body {
      font-family: 'Roboto', sans-serif;
      /*background: #E3D4C1;*/
      /*background: #000;*/
    }

rect {
      shape-rendering: crispEdges;
    }

text {
      /*text-shadow: 0 1px 0 #fff;*/
      font-size: 12px;
      /*font-family: 'Roboto', sans-serif;*/
      font-family: monospace;
      /*fill: white;*/
    }

.link {
      fill: none;
    }
  </style>
</head>

<body>

<h1>Sankey with circular links</h1>

let data = data2;

const nodePadding = 40;

const circularLinkGap = 2;

var sankey = d3.sankey()
      .nodeWidth(10)
      .nodePadding(nodePadding)
      .nodePaddingRatio(0.5)
      .scale(0.5)
      .size([width, height])
      .nodeId(function (d) {
        return d.name;
      })
      .nodeAlign(d3.sankeyJustify)
      .iterations(32);

var svg = d3.select("#chart").append("svg")
      .attr("width", width + margin.left + margin.right)
      .attr("height", height + margin.top + margin.bottom);

var g = svg.append("g")
      .attr("transform", "translate(" + margin.left + "," + margin.top + ")")

var linkG = g.append("g")
      .attr("class", "links")
      .attr("fill", "none")
      .attr("stroke-opacity", 0.2)
      .selectAll("path");

var nodeG = g.append("g")
      .attr("class", "nodes")
      .attr("font-family", "sans-serif")
      .attr("font-size", 10)
      .selectAll("g");

//run the Sankey + circular over the data
    let sankeyData = sankey(data);
    let sankeyNodes = sankeyData.nodes;
    let sankeyLinks = sankeyData.links;

let depthExtent = d3.extent(sankeyNodes, function (d) { return d.depth; });

var nodeColour = d3.scaleSequential(d3.interpolateCool)
    .domain([0,width]);

//Adjust link Y coordinates based on target/source Y positions

var node = nodeG.data(sankeyNodes)
      .enter()
      .append("g");

node.append("rect")
      .attr("x", function (d) { return d.x0; })
      .attr("y", function (d) { return d.y0; })
      .attr("height", function (d) { return d.y1 - d.y0; })
      .attr("width", function (d) { return d.x1 - d.x0; })
      .style("fill", function (d) { return nodeColour(d.x0); })
      .style("opacity", 0.5)
      .on("mouseover", function (d) {

let thisName = d.name;

node.selectAll("rect")
          .style("opacity", function (d) {
            return highlightNodes(d, thisName)
          })

d3.selectAll(".sankey-link")
          .style("opacity", function (l) {
            return l.source.name == thisName || l.target.name == thisName ? 1 : 0.3;
          })

node.selectAll("text")
          .style("opacity", function (d) {
            return highlightNodes(d, thisName)
          })
      })
      .on("mouseout", function (d) {
        d3.selectAll("rect").style("opacity", 0.5);
        d3.selectAll(".sankey-link").style("opacity", 0.7);
        d3.selectAll("text").style("opacity", 1);
      })

node.append("text")
      .attr("x", function (d) { return (d.x0 + d.x1) / 2; })
      .attr("y", function (d) { return d.y0 - 12; })
      .attr("dy", "0.35em")
      .attr("text-anchor", "middle")
      .text(function (d) { return d.name; });

node.append("title")
      .text(function (d) { return d.name + "\n" + (d.value); });

var link = linkG.data(sankeyLinks)
      .enter()
      .append("g")
    
    link.append("path") 
      .attr("class", "sankey-link")
      .attr("d", sankeyPath)
      .style("stroke-width", function (d) { return Math.max(1, d.width); })
      .style("opacity", 0.7)
      .style("stroke", function (link, i) {
        return link.circular ? "red" : "black"
      })

link.append("title")
      .text(function (d) {
        return d.source.name + " → " + d.target.name + "\n Index: " + (d.index);
      });

//ARROWS
    var arrowsG = linkG.data(sankeyLinks)
      .enter()
      .append("g")
      .attr("class", "g-arrow")
      .call(appendArrows, 10, 10, 4) //arrow length, gap, arrow head size

arrowsG.selectAll("path")
      .style("stroke-width", "10")
      //.style("stroke-dasharray", "10,10")

arrowsG.selectAll(".arrow-head").remove()

let duration = 5
    let maxOffset = 10;
    let percentageOffset = 1;

var animateDash = setInterval(updateDash, duration);

function updateDash() {

arrowsG.selectAll("path")
      .style("stroke-dashoffset", percentageOffset * maxOffset)

percentageOffset = percentageOffset == 0 ? 1 : percentageOffset - 0.01

}

function highlightNodes(node, name) {

let opacity = 0.3

if (node.name == name) {
        opacity = 1;
      }
      node.sourceLinks.forEach(function (link) {
        if (link.target.name == name) {
          opacity = 1;
        };
      })
      node.targetLinks.forEach(function (link) {
        if (link.source.name == name) {
          opacity = 1;
        };
      })

return opacity;

}

</script>
</body>

</html>

https://d3js.org/d3.v4.min.js

https://d3js.org/d3-scale-chromatic.v1.min.js