Handle URL anchor change event in js

Google Custom Search Engines use a timer to check the hash against a previous value, whilst the child iframe on a seperate domain updates the parent's location hash to contain the size of the iframe document's body. When the timer catches the change, the parent can resize the iframe to match that of the body so that scrollbars aren't displayed.

Something like the following achieves the same:

var storedHash = window.location.hash;
window.setInterval(function () {
    if (window.location.hash != storedHash) {
        storedHash = window.location.hash;
        hashChanged(storedHash);
    }
}, 100); // Google uses 100ms intervals I think, might be lower

Google Chrome 5, Safari 5, Opera 10.60, Firefox 3.6 and Internet Explorer 8 all support the hashchange event:

if ("onhashchange" in window) // does the browser support the hashchange event?
    window.onhashchange = function () {
        hashChanged(window.location.hash);
    }

and putting it together:

if ("onhashchange" in window) { // event supported?
    window.onhashchange = function () {
        hashChanged(window.location.hash);
    }
}
else { // event not supported:
    var storedHash = window.location.hash;
    window.setInterval(function () {
        if (window.location.hash != storedHash) {
            storedHash = window.location.hash;
            hashChanged(storedHash);
        }
    }, 100);
}

jQuery also has a plugin that will check for the hashchange event and provide its own if necessary - http://benalman.com/projects/jquery-hashchange-plugin/.

EDIT: Updated browser support (again).

I would recommend using addEventListener instead of overwriting window.onhashchange, otherwise you will block the event for other plugins.

window.addEventListener('hashchange', function() {
...
})

Looking at the global browser usage today, a fallback is not needed anymore.

From what I see in other SO questions, the only workable cross-browser solution is a timer. Check out this question for example.