D3 Examples - Point-Along-Path Interpolation

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<!DOCTYPE html>
<meta charset="utf-8">
<body>
<style>
​
path {
  fill: none;
  stroke: #000;
  stroke-width: 3px;
}
​
circle {
  fill: steelblue;
  stroke: #fff;
  stroke-width: 3px;
}
​
</style>
<script src="//d3js.org/d3.v3.min.js"></script>
<script>
​
var points = [
  [200, 200],
  [500, 200],
  [500, 400],
  [200, 400],
  
];
  var points2 = [
  [100, 200],
  [400, 200],
  [400, 400],
  [100, 400],
  
];
​
​
var svg = d3.select("body").append("svg")
    .attr("width", 960)
    .attr("height", 500);
​
var dataset = [];
  
var path = svg.append("path")
    .data([points])
    .attr("d", d3.svg.line()
    .tension(0) // Catmull–Rom
    .interpolate("cardinal-closed"));
​
var path2 = svg.append("path")
    .data([points2])
    .attr("d", d3.svg.line()
    .tension(0) // Catmull–Rom
    .interpolate("cardinal-closed"));
  
// OPTIONAL
svg.selectAll(".point")
    .data(points)
    .enter().append("circle")
    .attr("r", 4)
    .attr("transform", function(d) { return "translate(" + d + ")"; });
// OPTIONAL
  
/*
var circle = svg.append("circle")
    .attr("r", 13)
    .attr("transform", "translate(" + points[0] + ")");
*/
  
  
    d3.select("svg").on("click", function()
         {
            // get the mouse position coordinates
            var coordinates = [0, 0];
            coordinates = d3.mouse(this);
            var x = coordinates[0];
            var y = coordinates[1];
​
            dataset.push(10);
​
            var circles = svg.selectAll("circle")   //Select all circles
                              .data(dataset);
​
            circles.enter()
                    .append("circle")
                    .attr({cx:x, cy:y, fill:"red"})
                        .attr("r", function(d){return d})
                            .attr("transform", "translate(" + points[0] + ")")
​
​
          
​
transition();
​
function transition() {
  circles.transition()
      .duration(10000)
      .attrTween("transform", translateAlong(path.node()))
      .each("end", transition);
}
      
      
      
      });
​
// Returns an attrTween for translating along the specified path element.
function translateAlong(path) {
  var l = path.getTotalLength();
  return function(d, i, a) {
    return function(t) {
      var p = path.getPointAtLength(t * l);
      return "translate(" + p.x + "," + p.y + ")";
    };
  };
}
​
​
</script>
​
    