Finding the data transformation

// based on basic block builder template
<!DOCTYPE html>
<head>
  <meta charset="utf-8">
  <script src="https://cdnjs.cloudflare.com/ajax/libs/d3/3.5.5/d3.min.js"></script>
  <style>
    body { margin:0;position:fixed;top:0;right:0;bottom:0;left:0; }
    svg { width: 100%; height: 100%; }
  </style>
</head>

<body>
  <script>
    var margin = {top: 20, right: 10, bottom: 20, left: 10};
    var width = 980 - margin.left - margin.right;
    var height = 500 - margin.top - margin.bottom;
    var svg = d3.select("body").append("svg")
    	.attr("width", width + margin.left + margin.right)
     	.attr("height", height + margin.top + margin.bottom)
    	.append("g")
      		.attr("transform", "translate(" + margin.left + "," + margin.top + ")");
       
    var links = [
  		"mbostock/3885304",
  		"zanarmstrong/5fbc4b93f62227dedeb7",
  		"zanarmstrong/d6ffcd5b9839629efaa9"
  	]

var regEx = /(\w+)\/(\w+)/

svg.selectAll("image").data(links).enter().append("image")
        .attr("xlink:href",  function(d) { return "https://bl.ocks.org/" + regEx.exec(d)[1] + "/raw/" + regEx.exec(d)[2] + "/thumbnail.png";})
        .attr("x", function(d, i) { return (i % 5)*188;})
        .attr("y", function(d, i){return Math.floor(i / 5)*100})
        .attr("height", 100)
        .attr("width", 180)
        .on("click", function(d){window.open("https://blockbuilder.org/" + d)});
    
  </script>
</body>

https://cdnjs.cloudflare.com/ajax/libs/d3/3.5.5/d3.min.js