D3 Examples - Transitions

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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>
  
  <button>Update</button>
  
  <script>
    
    let data1 = [1,2,3,4,5,6,7,8,9,10]; //ENTER ALL
    let data2 = [1,1,3,4,6,7,9,10];  //EXIT 2, 5, 8
    let data3 = [1,2,3,4,5,6,7,9]; //ENTER 2, 5; EXIT 8, 10
    
    let radius = 25;
    let duration = 5000;
    
    var svg = d3.select("body").append("svg")
      .attr("width", 960)
      .attr("height", 500)
​
    update(data1);
    
    function update(data) {
      
      let circles = svg.selectAll("circle")
        .data(data, function(d){ return d; });
      
      let enter = circles.enter()
        .append("circle")
        .style("opacity", 0)
        .style("fill", "blue")
        .attr("r", radius)
        .attr("cy", 25)
        .attr("cx", function(d){ return 55 * d })
      
      let exit = circles.exit();
      
      let merge = circles.merge(enter)
        .transition()
        .duration(duration)
        .style("opacity", 1)
      
      exit.transition()
        .duration(duration)
        .style("opacity", 0)
        .remove();
​
    };
    
    let currentData = 1;
    
    d3.select("button")
        .on("click", function(){
        if (currentData == 1) {
          update(data2);
                    currentData = 2;
        } else if (currentData == 2) {
          update(data3);
          currentData = 3;
        } else if (currentData == 3) {
          update(data1);
          currentData = 1;
        }  ;
    })
​
  </script>
</body>
​
    