SwoopyArrowTest

<!DOCTYPE html>
<head>
  <meta charset="utf-8">
  <script src="https://d3js.org/d3.v4.min.js"></script>
  <style>
    body { margin:0;position:fixed;top:0;right:0;bottom:0;left:0; }
    
    .swoopyArrow{
      fill:none;
      stroke:black;
     }
    
  </style>
</head>
<svg>
<marker id="arrowhead" viewBox="-10 -10 20 20" refX="0" refY="0" markerWidth="20" markerHeight="20" stroke-width="1" orient="auto"><polyline stroke-linejoin="bevel" points="-6.75,-6.75 0,0 -6.75,6.75"></polyline></marker>
</svg>
<script src="SwoopyArrow.js"></script>
<body>
  <script>
    
    //https://github.com/bizweekgraphics/swoopyarrows

var svg = d3.select("svg")
      .attr("width", 500)
      .attr("height", 500)
	    .style("outline","1px solid black")
    	.style("margin","50px")
    
    svg.append("circle")
      .attr("cy", 200)
      .attr("cx", 120)
    	.attr("r",5)
    	.style("fill","black")
      .attr("font-size", 36)
      .attr("font-family", "monospace")
	
    var swoopy = swoopyArrow()
  		.angle(Math.PI/2)
  		.x(function(d) { return d[0]; })
  		.y(function(d) { return d[1]; });

svg.append("path")
    	.attr("class","swoopyArrow")
      .attr('marker-end', 'url(#arrowhead)')
      .datum([[250,200],[130,205]])
      .attr("d", swoopy);
    
  </script>
</body>

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