D3 Examples - Loading Circle V0 - Multiple Circles & Movement

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<!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>
    const width = 960;
    const height = 500;
    
    const midWidth = Math.floor(width/2);
        const midHeight = Math.floor(height/2);
    
    const color = d3.scaleOrdinal(d3.schemeCategory10);
    
    function getIn(transition) {
      transition.duration(2500)
        .ease(d3.easeExp)
        .attr("cx", midWidth + 50)
        .attr("r", 20)
        .on("end", function() {
            d3.select(this).transition().call(firstRotateClockwise);
        });
    }
    
    function getOut(transition) {
      transition.duration(2500)
        .ease(d3.easeExp)
        .attr("cx", midWidth)
        .attr("r", 0)
        .on("end", function() {
            d3.select(this).transition().delay(5000).call(getIn);
        });
    }
    
    function firstRotateClockwise(transition) {
      transition.duration(5000)
        .ease(d3.easeBackIn)
            .attrTween("cx", function() {
            return function(t) {
            return(midWidth + 50 * Math.cos(2 * Math.PI * t));
          }
            })
        .attrTween("cy", function() {
          return function(t) {
            return(midHeight + 50 * Math.sin(2 * Math.PI * t));
          }
        }).on("end", function() {
            d3.select(this)
            .attr("lap", 1)
            .transition().call(rotateClockwise);
        });
    }
    
    function rotateClockwise(transition) {
      transition.duration(1500)
        .ease(d3.easeLinear)
            .attrTween("cx", function() {
            return function(t) {
            return(midWidth + 50 * Math.cos(2 * Math.PI * t));
          }
            })
        .attrTween("cy", function() {
          return function(t) {
            return(midHeight + 50 * Math.sin(2 * Math.PI * t));
          }
        }).on("end", function() {
            let lap = parseFloat(d3.select(this).attr("lap")) + 1;
            if(lap != 10) 
            d3.select(this).attr("lap", lap)
                .transition().call(rotateClockwise);
            else 
            d3.select(this).transition().call(getOut);
        });
    }
       
    const svg = d3.select("body").append("svg")
        .attr("width", width)
      .attr("height", height);
​
    for(let i=0 ; i<3 ; i++) {
      svg.append("circle")
        .attr("cx", midWidth)
        .attr("cy", midHeight)
        .attr("r", 0)
        .attr("fill", color(i))
        .attr("lap", 0)
        .transition().delay(500 * i).call(getIn);
    }
  </script>
</body>
​
    