d3-bring-to-front.js

// Credit Christopher Chiche & Clemens Tolboom
// - http://stackoverflow.com/a/14426477/2806996
d3.selection.prototype.moveToFront = function() {
  return this.each(function(){
    this.parentNode.appendChild(this);
  });
};

d3.selection.prototype.moveToBack = function() { 
    return this.each(function() { 
        var firstChild = this.parentNode.firstChild; 
        if (firstChild) { 
            this.parentNode.insertBefore(this, firstChild); 
        } 
    }); 
};