window.onload = function() {

        var menuID = 'navigation'; // The ID of your menu
        var activeClass = 'menuactive'; // The class to add

        var menu = document.getElementById(menuID);
        var items = menu.getElementsByTagName('a');
        for( var i = 0; i < items.length; i++ ) {
            if( items[i].href.replace(/https?:\/\/.*?\//i , '/') == 
                location.href.replace(/https?:\/\/.*?\//i , '/') ) {
                items[i].parentNode.className = activeClass;
                break;
            }
        }

};