Moving along path practice

_.md

[ Launch: Tributary inlet ] 6133395 by tarvaina

config.json

{"description":"Moving along path practice","endpoint":"","display":"svg","public":true,"require":[],"fileconfigs":{"inlet.js":{"default":true,"vim":false,"emacs":false,"fontSize":12},"_.md":{"default":true,"vim":false,"emacs":false,"fontSize":12},"config.json":{"default":true,"vim":false,"emacs":false,"fontSize":12}},"fullscreen":false,"play":false,"loop":false,"restart":false,"autoinit":true,"pause":true,"loop_type":"period","bv":false,"nclones":15,"clone_opacity":0.4,"duration":3000,"ease":"linear","dt":0.01,"thumbnail":"http://i.imgur.com/biW4n8M.png"}

inlet.js

var data = [
  {x: 120, y:40},
  {x: 356, y:76},
  {x: 26, y:120},  
  {x: 60, y:193},
  {x: 26, y:318}  
];

var line = d3.svg.line()
  .x(function(v) { return v.x; })
  .y(function(v) { return v.y; });

var svg = d3.select("svg");

var group = svg.append("g")
  .attr({
    transform: "translate(" + [50, 50] + ")"
  });

var path = group.selectAll("path").data([data]).enter()
  .append("path")
  .attr({
    d: line,
    fill: "none",
    stroke: "#000000"
  });

var pathLength = path.node().getTotalLength();

path.attr({
    "stroke-dasharray": pathLength + " " + pathLength,
    "stroke-dashoffset": pathLength  
});

var circlePosition = function(t) {
  return path.node().getPointAtLength(pathLength * t);
};

var pos = circlePosition(0);

var circle = group.selectAll("circle").data([data]).enter()
  .append("circle")
  .attr({
    r: 20,
    cx: pos.x,
    cy: pos.y
  });


svg.on("click", function() {
  var dur = 2000;
  var ease = "bounce";
  
  path
    .transition()
    .duration(dur)
    .ease(ease)
    .attrTween(
      "stroke-dashoffset",
      function(d, i, a) {
        return function(t) {
          return pathLength * (1 - t);
        };
      });
  circle
    .transition()
    .duration(dur)
    .ease(ease)
    .attrTween(
      "cx",
      function(d, i, a) {
        return function(t) { return circlePosition(t).x };
      })
    .attrTween(
      "cy",
      function(d, i, a) {
        return function(t) { return circlePosition(t).y };
      });
});