Is My Page Being Loaded from the Browser Cache?

Navigation Timing is in most browsers now(ie9+) http://www.w3.org/TR/navigation-timing/#sec-navigation-info-interface

 if (!!window.performance && window.performance.navigation.type === 2) {
   // page has been hit using back or forward buttons
 } else {
   // regular page hit
 }

You can ask the web browser to not cache the page. Try these HTTP headers:

Cache-control: no-cache
Cache-control: no-store
Pragma: no-cache
Expires: 0

Particularly, Cache-control: no-store is interesting because it tells the browser to not store the page in memory at all which prevents a stale page being loaded when you hit the back/forward button.

If you do this instead, you don't have to poll for data on page load.