selection.order by NelsonMinar

index.html

<!DOCTYPE html>
<html>
  <head>
    <meta http-equiv="Content-Type" content="text/html;charset=utf-8"/>
  </head>
  <body>
    <script type="text/javascript" src="//mbostock.github.com/d3/d3.js?2.6.0"></script>
    <script type="text/javascript">

d3.selection.prototype.order = function() {
  for (var j = 0, m = this.length; j < m; j++) {
    for (var group = this[j], i = 1, n = group.length, prev = group[0]; i < n; i++) {
      var node = group[i];
      if (node) {
        if (prev) prev.parentNode.insertBefore(node, prev.nextSibling);
        prev = node;
      }
    }
  }
  return this;
};

var div = d3.select("body").selectAll("div")
    .data(["a", "b", "f"], String)
  .enter().append("div")
    .text(String);
div.order();

var div = d3.select("body").selectAll("div")
    .data(["a", "b", "c", "d", "e", "f"], String);

div.enter().append("div")
    .text(String);

div.order();

    </script>
  </body>
</html>