Circles_1

<!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; }
  </style>
</head>

<body>
  <script>
//setup elements
 var circleData = [
  { "cx": 20, "cy": 20, "radius": 20, "color" : "green" },
  { "cx": 70, "cy": 70, "radius": 20, "color" : "purple" }];

var rectangleData = [
  { "rx": 110, "ry": 110, "height": 30, "width": 30, "color" : "blue" },
  { "rx": 160, "ry": 160, "height": 30, "width": 30, "color" : "red" }];

var svgContainer = d3.select("body").append("svg")
                                     .attr("width",300)
                                     .attr("height",300);

// Append an SVG group element to the svg container
var circleGroup = svgContainer.append("g");

//put the circles in the group and not in the svgContainer like done before
var circles = circleGroup.selectAll("circle")
                          .data(circleData)
                          .enter()
                          .append("circle");

</script>
</body>

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