index.html

<!DOCTYPE html>
<script src="https://cdn.jsdelivr.net/npm/d3-require@1"></script>
<script>

  function loadFile(filePath) {
    // Inspired by https://stackoverflow.com/a/41133213 (therefore original license is CC BY-SA 3.0)
    var result = null;
    var xmlhttp = new XMLHttpRequest();
    xmlhttp.open("GET", filePath, false);
    xmlhttp.send();
    if (xmlhttp.status == 200) {
      result = xmlhttp.responseText;
    } else {
      alert("Error loading diagram data file '" + filePath + "' [http status " + xmlhttp.status + "]");
    }
    return result;
  }

  (async () => {
    /*
      Ported from https://observablehq.com/@d3/sankey-diagram@278
      Copyright 2018–2020 Observable, Inc.
      Permission to use, copy, modify, and/or distribute this software for any
      purpose with or without fee is hereby granted, provided that the above
      copyright notice and this permission notice appear in all copies.
      THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
      WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
      MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
      ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
      WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
      ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
      OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
    */
    const d3 = await window.d3.require("d3@6", "d3-sankey@0.12");

    const width = 954;
    const height = 600;
    const align = "justify";
    const edgeColor = "path";

    const color = (() => {
      const color = d3.scaleOrdinal(d3.schemeCategory10);
      return d => color(d.category === undefined ? d.name : d.category);
    })();

    data = (() => {
      // modified from original code to load data from separate file instead of inline
      const links = d3.csvParse(loadFile("./data.csv"), d3.autoType);
      const nodes = Array.from(new Set(links.flatMap(l => [l.source, l.target])), name => ({ name, category: name.replace(/ .*/, "") }));
      return { nodes, links, units: "relationship points" };
    })();

    const format = (() => {
      const format = d3.format(",.0f");
      return data.units ? d => `${format(d)} ${data.units}` : format;
    })();

    const sankey = (() => {
      const sankey = d3.sankey()
        .nodeId(d => d.name)
        .nodeAlign(d3[`sankey${align[0].toUpperCase()}${align.slice(1)}`])
        .nodeWidth(15)
        .nodePadding(10)
        .extent([[1, 5], [width - 1, height - 5]]);
      return ({ nodes, links }) => sankey({
        nodes: nodes.map(d => Object.assign({}, d)),
        links: links.map(d => Object.assign({}, d))
      });
    })();

    const chart = (() => {
      const svg = d3.create("svg")
        .attr("viewBox", [0, 0, width, height]);

      const { nodes, links } = sankey(data);

      svg.append("g")
        .attr("stroke", "#000")
        .selectAll("rect")
        .data(nodes)
        .join("rect")
        .attr("x", d => d.x0)
        .attr("y", d => d.y0)
        .attr("height", d => d.y1 - d.y0)
        .attr("width", d => d.x1 - d.x0)
        .attr("fill", color)
        .append("title")
        .text(d => `${d.name}\n${format(d.value)}`);

      const link = svg.append("g")
        .attr("fill", "none")
        .attr("stroke-opacity", 0.5)
        .selectAll("g")
        .data(links)
        .join("g")
        .style("mix-blend-mode", "multiply");

      if (edgeColor === "path") {
        const gradient = link.append("linearGradient")
          .attr("id", (d, i) => (d.uid = `link-${i}`))
          .attr("gradientUnits", "userSpaceOnUse")
          .attr("x1", d => d.source.x1)
          .attr("x2", d => d.target.x0);

        gradient.append("stop")
          .attr("offset", "0%")
          .attr("stop-color", d => color(d.source));

        gradient.append("stop")
          .attr("offset", "100%")
          .attr("stop-color", d => color(d.target));
      }

      link.append("path")
        .attr("d", d3.sankeyLinkHorizontal())
        .attr("stroke", d => edgeColor === "none" ? "#aaa"
          : edgeColor === "path" ? `url(#${d.uid})`
            : edgeColor === "input" ? color(d.source)
              : color(d.target))
        .attr("stroke-width", d => Math.max(1, d.width));

      link.append("title")
        .text(d => `${d.source.name} → ${d.target.name}\n${format(d.value)}`);

      svg.append("g")
        .attr("font-family", "sans-serif")
        .attr("font-size", 10)
        .selectAll("text")
        .data(nodes)
        .join("text")
        .attr("x", d => d.x0 < width / 2 ? d.x1 + 6 : d.x0 - 6)
        .attr("y", d => (d.y1 + d.y0) / 2)
        .attr("dy", "0.35em")
        .attr("text-anchor", d => d.x0 < width / 2 ? "start" : "end")
        .text(d => d.name);

      return svg.node();
    })();
    document.body.appendChild(chart);

  })()
</script>