Is there a cross-browser onload event when clicking the back button?

Question

For all major browsers (except IE), the JavaScript onload event doesn’t fire when the page loads as a result of a back button operation — it only fires when the

Answer 1

Some modern browsers (Firefox, Safari, and Opera, but not Chrome) support the special "back/forward" cache (I'll call it bfcache, which is a term invented by Mozilla), involved when the user navigates Back. Unlike the regular (HTTP) cache, it captures the complete state of the page (including the state of JS, DOM). This allows it to re-load the page quicker and exactly as the user left it.

The load event is not supposed to fire when the page is loaded from this bfcache. For example, if you created your UI in the "load" handler, and the "load" event was fired once on the initial load, and the second time when the page was re-loaded from the bfcache, the page would end up with duplicate UI elements.

This is also why adding the "unload" handler stops the page from being stored in the bfcache (thus making it slower to navigate back to) -- the unload handler could perform clean-up tasks, which could leave the page in unworkable state.

For pages that need to know when they're being navigated away/back to, Firefox 1.5+ and the version of Safari with the fix for bug 28758 support special events called "pageshow" and "pagehide".

References:

• Webkit: http://webkit.org/blog/516/webkit-page-cache-ii-the-unload-event/
• Firefox: https://developer.mozilla.org/En/Using_Firefox_1.5_caching.
• Chrome: https://code.google.com/p/chromium/issues/detail?id=2879