Как создать SVG дуги между двумя точками

function arc_links(dwg,x1,y1,x2,y2,n,k) {
  var cx = (x1+x2)/2;
  var cy = (y1+y2)/2;
  var dx = (x2-x1)/2;
  var dy = (y2-y1)/2;
  var i;
  for (i=0; i<n; i++) {
    if (i==(n-1)/2) {
      dwg.line(x1,y1,x2,y2).stroke({width:1}).fill('none');
    }
    else {
      dd = Math.sqrt(dx*dx+dy*dy);
      ex = cx + dy/dd * k * (i-(n-1)/2);
      ey = cy - dx/dd * k * (i-(n-1)/2);
      dwg.path("M"+x1+" "+y1+"Q"+ex+" "+ey+" "+x2+" "+y2).stroke({width:1}).fill('none');
    }
  }
}

function create_svg() {
  var draw = SVG('drawing').size(300, 300);
  arc_links(draw,50,50,250,50,2,40);
  arc_links(draw,250,50,250,250,3,40);
  arc_links(draw,250,250,50,250,4,40);
  arc_links(draw,50,250,50,50,5,40);
  draw.circle(50).move(25,25).fill('#fff').stroke({width:1});
  draw.circle(50).move(225,25).fill('#fff').stroke({width:1});
  draw.circle(50).move(225,225).fill('#fff').stroke({width:1});
  draw.circle(50).move(25,225).fill('#fff').stroke({width:1});
}

create_svg();

<script src="https://cdnjs.cloudflare.com/ajax/libs/svg.js/2.3.2/svg.min.js"></script>
<div id="drawing"></div>

let r = (d, x) => !x?1e10:0.125*d*d/x + x/2; 

upd();

function upd() {
  let n = +count.value;
  let s = +step.value/10;
  let x1 = c1.getAttribute('cx'), y1 = c1.getAttribute('cy');
  let x2 = c2.getAttribute('cx'), y2 = c2.getAttribute('cy');
  let dx = Math.sqrt((x1-x2)*(x1-x2) + (y1-y2)*(y1-y2));
  paths.innerHTML = [...Array(n)].map((_, i) => [
    n%2&&i===n-1?0:1+parseInt(i/2),
    i%2
  ]).map(i => `<path d="${[
    'M', x1, y1,
    'A', r(dx, s*i[0]), r(dx, s*i[0]), 0, 0, i[1], x2, y2
  ].join(' ')}"></path>`).join('');
}

<input id="count" type="range" min=1 max=9 value=5 oninput=upd() >
<input id="step" type="range" min=1 max=200 value=100 oninput=upd() >
<svg viewbox=0,0,300,100 stroke=red fill=none >
  <circle id=c1 r=10 cx=50 cy=60></circle>
  <circle id=c2 r=10 cx=250 cy=40></circle>
  <g id=paths></g>
</svg>

var divA       = document.querySelector("#a");
var divB       = document.querySelector("#b");
var arrowLeft  = document.querySelector("#arrowLeft");
var arrowRight = document.querySelector("#arrowRight");

var drawConnector = function() {
  var posnALeft = {
    x: divA.offsetLeft - 8,
    y: divA.offsetTop  + divA.offsetHeight / 2
  };
  var posnARight = {
    x: divA.offsetLeft + divA.offsetWidth + 8,
    y: divA.offsetTop  + divA.offsetHeight / 2    
  };
  var posnBLeft = {
    x: divB.offsetLeft - 8,
    y: divB.offsetTop  + divA.offsetHeight / 2
  };
  var posnBRight = {
    x: divB.offsetLeft + divB.offsetWidth + 8,
    y: divB.offsetTop  + divA.offsetHeight / 2
  };
  var dStrLeft =
      "M" +
      (posnALeft.x      ) + "," + (posnALeft.y) + " " +
      "C" +
      (posnALeft.x - 100) + "," + (posnALeft.y) + " " +
      (posnBLeft.x - 100) + "," + (posnBLeft.y) + " " +
      (posnBLeft.x      ) + "," + (posnBLeft.y);
  arrowLeft.setAttribute("d", dStrLeft);
  var dStrRight =
      "M" +
      (posnBRight.x      ) + "," + (posnBRight.y) + " " +
      "C" +
      (posnBRight.x + 100) + "," + (posnBRight.y) + " " +
      (posnARight.x + 100) + "," + (posnARight.y) + " " +
      (posnARight.x      ) + "," + (posnARight.y);
  arrowRight.setAttribute("d", dStrRight);
};

$("#a, #b").draggable({
  drag: function(event, ui) {
    drawConnector();
  }
});

setTimeout(drawConnector, 250);

html,
body {
  width: 100%;
  height: 100%;
  padding: 0;
  margin: 0;
}
#instructions {
  position: fixed;
  left: 50%;
}
#a, #b {
  color: white;
  text-align: center;
  padding: 10px;
  position: fixed;
  width: 100px;
  height: 20px;
  left: 100px;
}
#a {
  background-color: blue;
  top: 20px;
}
#b {
  background-color: red;
  top: 180px;
}

<p id="instructions">Нажмите и перетащите любой div, чтобы увидеть непроизвольную установку стрелок.</p>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<script src="https://ajax.googleapis.com/ajax/libs/jqueryui/1.12.0/jquery-ui.min.js"></script>
<svg xmlns="http://www.w3.org/2000/svg" width="100%" height="100%">
  <defs>
    <marker id="arrowhead" viewBox="0 0 10 10" refX="3" refY="5"
        markerWidth="6" markerHeight="6" orient="auto">
      <path d="M 0 0 L 10 5 L 0 10 z" />
    </marker>
  </defs>
  <g fill="none" stroke="black" stroke-width="2" marker-end="url(#arrowhead)">
    <path id="arrowLeft"/>
    <path id="arrowRight"/>
  </g>
</svg>
<div id="a">Div 1</div>
<div id="b">Div 2</div>