how to detect back button pressed in browser using javascript code example

Example: detect back button press javascript

So as far as AJAX is concerned...

Pressing back while using most web-apps that use AJAX to navigate specific parts of a page is a HUGE issue. I don't accept that 'having to disable the button means you're doing something wrong' and in fact developers in different facets have long run into this problem. Here's my solution:

window.onload = function () {
    if (typeof history.pushState === "function") {
        history.pushState("jibberish", null, null);
        window.onpopstate = function () {
            history.pushState('newjibberish', null, null);
            // Handle the back (or forward) buttons here
            // Will NOT handle refresh, use onbeforeunload for this.
        };
    }
    else {
        var ignoreHashChange = true;
        window.onhashchange = function () {
            if (!ignoreHashChange) {
                ignoreHashChange = true;
                window.location.hash = Math.random();
                // Detect and redirect change here
                // Works in older FF and IE9
                // * it does mess with your hash symbol (anchor?) pound sign
                // delimiter on the end of the URL
            }
            else {
                ignoreHashChange = false;   
            }
        };
    }
}
As far as Ive been able to tell this works across chrome, firefox, haven't tested IE yet.