This should contain the stand alone code for the tumbnails, and their related functionality

thumbnails.js

// 
// The code in this file should: 
// - build a thumbnail container
// - populate the container with thumbnails
// - when a thumbnail is clicked, the main image should be updated with the appropriate image
//
// This code should be optional, and initiate itself if included.
//
(function(){
  var thumbContainer = document.createDocumentFragment();
  var thumbWrapper = document.createElement('div');
  thumbWrapper.setAttribute('id','thumb-wrapper');
  thumbContainer.appendChild(thumbWrapper);
  document.body.appendChild(thumbContainer);
})();

viewport.js

// 
// The code in this file should: 
// - built itself a viewport that will contain the medium images.
// - Update itself when/if a thumbnail is clicked.
// - provide the ability to have external elements switch images.
//
// This code should be optional, and initiate itself if included.
//

(function(){
  var viewportContainer = document.createDocumentFragment();
  var viewportWrapper = document.createElement('div');
  viewportWrapper.setAttribute('id','viewport-wrapper'); 
  viewportContainer.appendChild(viewportWrapper);
  document.body.appendChild(viewportContainer);
})();