Accordion show open with the current url

sample.html

<nav class="main-nav">
        <ul>
            <li>
                <a href="/escola" title="" class="home">
                    <i></i>
                    <span>Início</span>
                </a>
            </li>

            <li class="dropdown">
                <a href="" title="" class="ballon">
                    <i></i>
                    <span>Cadastros</span>
                </a>

                <ul>
                    <li>
                        <a href="/editar-escola" title="" class="posts">Meu cadastro</a>
                    </li>
                    <li>
                        <a href="/escola/novo-atleta">Novo cadastro</a>
                    </li>
                    <li>
                        <a href="/escola/atletas">Pessoas cadastradas</a>
                    </li>
                </ul>
            </li>

            <li class="dropdown">
                <a href="" title="" class="paper">
                    <i></i>
                    <span>Espaços</span>
                </a>

                <ul>
                    <li>
                        <a href="/escola/espacos" title="" class="posts">Espaços cadastrados</a>
                    </li>
                    <li>
                        <a href="/escola/novo-auditorio">Novo espaço</a>
                    </li>
                </ul>
            </li>

            <li class="dropdown">
                <a href="" title="" class="ballon active">
                    <i></i>
                    <span>Mensagens</span>
                </a>

                <ul style="display: block; ">
                    <li>
                        <a href="/escola/mensagens" class="current">Todas as mensagens</a>
                    </li>

                    <li>
                        <a href="/escola/nova-mensagem">Nova mensagem</a>
                    </li>
                </ul>
            </li>

            <li class="dropdown">
                <a href="" title="" class="paper">
                    <i></i>
                    <span>Agenda</span>
                </a>
                <ul>
    <li>
        <a href="/escola/agenda/auditorio/5/31-07-2012">Auditório (Fernando Pessoa)</a>
    </li>
    <li>
        <a href="/escola/agenda/piscina/4/31-07-2012">Piscina (Semi)</a>
    </li>
    <li>
        <a href="/escola/agenda/quadra/6/31-07-2012">Quadra (Antônio Souza)</a>
    </li>
    <li>
        <a href="/escola/agenda/ginasio/2/31-07-2012">Ginásio (A#)</a>
    </li>
</ul>            </li>
        </ul>
    </nav>

urldropdown

/*=====[ =URLDropdown ]=====*/
    $(function(){
    var url = window.location.pathname,
        urlRegExp = new RegExp(url.replace(/\/$/,'') + "$"); // create regexp to match current url pathname and remove trailing slash if present as it could collide with the link in navigation in case trailing slash wasn't present there
        // now grab every link from the navigation
        $('.dropdown ul li a').each(function(){
            // and test its normalized href against the url pathname regexp
            if(urlRegExp.test(this.href.replace(/\/$/,''))){
                $(this).addClass('current');
                $currentUl = $(this).closest('ul'); // find selected accordion
                $currentUl.show(); // mostra
                $currentUl.closest('.dropdown').children('a').addClass('active'); // add class current to active link
            }
        });
    });