Full Document height calculation:
To be more generic and find the height of any document you could just find the highest DOM Node on current page with a simple recursion:
;(function() {
var pageHeight = 0;
function findHighestNode(nodesList) {
for (var i = nodesList.length - 1; i >= 0; i--) {
if (nodesList[i].scrollHeight && nodesList[i].clientHeight) {
var elHeight = Math.max(nodesList[i].scrollHeight, nodesList[i].clientHeight);
pageHeight = Math.max(elHeight, pageHeight);
}
if (nodesList[i].childNodes.length) findHighestNode(nodesList[i].childNodes);
}
}
findHighestNode(document.documentElement.childNodes);
// The entire page height is found
console.log('Page height is', pageHeight);
})();
You can Test it on your sample sites (http://fandango.com/ or http://paperbackswap.com/) with pasting this script to a DevTools Console.
NOTE: it is working with Iframes
.
Enjoy!