Got through the basics of the request functions. Hit d3.ns as well but

will probably loop back around.

src/core/html.js

@@ -1,3 +1,4 @@
+//A wrapper around d3.text that sets the MIME type to HTML and then handles the edge case of the responseText being empty. 
 d3.html = function(url, callback) {
   d3.text(url, "text/html", function(text) {
     if (text != null) { // Treat empty string as valid HTML.

src/core/json.js

@@ -1,3 +1,4 @@
+//A wrapper around d3.text that sets the MIME type to JSON and then parses the JSON before passing it to the callback. 
 d3.json = function(url, callback) {
   d3.text(url, "application/json", function(text) {
     callback(text ? JSON.parse(text) : null);

src/core/ns.js

@@ -1,3 +1,5 @@
+//Used for SVG namespacing. Mostly an internal method that is used before appending SVG elements to the page. 
+//TODO: better explanation of what is going on. 
 var d3_nsPrefix = {
   svg: "http://www.w3.org/2000/svg",
   xhtml: "http://www.w3.org/1999/xhtml",

src/core/text.js

@@ -1,3 +1,4 @@
+//A wrapper around d3.xhr that passes back the responseText of the response to the callback. 
 d3.text = function(url, mime, callback) {
   function ready(req) {
     callback(req && req.responseText);

src/core/xml.js

@@ -1,3 +1,4 @@
+//A wrapper around d3.xhr that grabs the responseXML from the response and then calls the callback. Similiar to d3.text in terms of scope. 
 d3.xml = function(url, mime, callback) {
   function ready(req) {
     callback(req && req.responseXML);