remove last directory in URL

I am trying to remove the last directory part of an URL. My URL looks like this:

https://my_ip_address:port/site.php?path=/path/to/my/folder.

When clicking on a button, I want to change this to

https://my_ip_address:port/site.php?path=/path/to/my. (Remove the last part).

I already tried window.location.replace(//[A-Za-z0-9%]+$/, ""), which results in

https://my_ip_address:port/undefined.

What Regex should I use to do this?

Answer

Explanation: Explode by “/”, remove the last element with pop, join again with “/”.

function RemoveLastDirectoryPartOf(the_url)
{
    var the_arr = the_url.split('/');
    the_arr.pop();
    return( the_arr.join('/') );
}

see fiddle http://jsfiddle.net/GWr7U/