calculateDocumentHeight.js

/**
 * Calculate the height of the document.
 * http://stackoverflow.com/questions/1145850/get-height-of-entire-document-with-javascript
 */
function calculateDocumentHeight() {
  var body = document.body,
      html = document.documentElement,
      height;
  height = Math.max( body.scrollHeight, body.offsetHeight, html.clientHeight, html.scrollHeight, html.offsetHeight );
  return height;
}