如何部分或仅按百分比沿路径过渡

var points = [
     [240, 100],
     [290, 200],
     [340, 50],
     [390, 150],
     [90, 150],
     [140, 50],
     [190, 200]
 ];

 var svg = d3.select("body").append("svg")
     .attr("width", 500)
     .attr("height", 300);

 var path = svg.append("path")
     .data([points])
     .attr("d", d3.svg.line()
         .tension(0) // Catmull–Rom
         .interpolate("cardinal-closed"));

 var color = d3.scale.category10();

 var data = [0.9, 1, 0.8, 0.75, 1.2];

 svg.selectAll(".point")
     .data(points)
     .enter().append("circle")
     .attr("r", 4)
     .attr("transform", function(d) {
         return "translate(" + d + ")";
     });

 var circle = svg.selectAll("foo")
     .data(data)
     .enter()
     .append("circle")
     .attr("r", 13)
     .attr("fill", function(d, i) {
         return color(i)
     })
     .attr("transform", "translate(" + points[0] + ")");


 circle.transition()
     .duration(10000)
     .attrTween("transform", function(d) {
         return translateAlong(d, path.node())()
     });

 // Returns an attrTween for translating along the specified path element.
 function translateAlong(d, path) {
     var l = path.getTotalLength() * d;
     return function(d, i, a) {
         return function(t) {
             var p = (t * l) < path.getTotalLength() ?
                 path.getPointAtLength(t * l) : path.getPointAtLength(t * l - path.getTotalLength());
             return "translate(" + p.x + "," + p.y + ")";
         };
     };
 }

path {
  fill: none;
  stroke: #000;
  stroke-width: 3px;
}
    
circle {
  stroke: #fff;
  stroke-width: 3px;
}

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