chart = {
  const svg = d3.create("svg").attr("viewBox", [0, 0, 900, 610]);

  svg
    .append("g")
    .attr("transform", "translate(610,20)")
    .append(() =>
      legend({
        color: prevScale,
        title: 'Prev. of Obesity (%)',
        width: 260
      })
    );

  svg
    .append("g")
    .selectAll("path")
    .data(topojson.feature(TJHD_ZCTAs, TJHD_ZCTAs.objects.TJHD_ZCTAs).features)
    .join("path")
    .attr('stroke', '#404040')
+
    .attr('fill', 'white')
    .attr("d", path)
    .attr("class", "ZCTA")
-
    .append("title")
    .text(
      d =>
        `${d.properties.ZCTA5CE10}: ${prev_by_ZCTA.get(
          d.properties.ZCTA5CE10
        ) || '-'}\%`
    );
+
    .append("title");

  return svg.node();
}

d3
+
  .select(chart)
  .selectAll('.ZCTA')
  .transition()
  .attr(
    "fill",
    d => prevScale(prev_by_ZCTA.get(d.properties.ZCTA5CE10)) || "white"
  )
-
  .duration(2000)
+
  .select("title")
  .text(
    d =>
      `${d.properties.ZCTA5CE10}: ${prev_by_ZCTA.get(
        d.properties.ZCTA5CE10
      ) || '-'}\%`
  )