Select next <div /> once you know the closest selector with javascript

I am developing a website and I can't use jQuery (no discussion about this), so pure javascript and a custom javascript framework is used.

Actually I have found a situation that I don't know how to handle:

I've a group of selectors, that for each one I add a "onclick" event to display / hide a div.

For example:

<div id="menu">
    开发者_JS百科<div class="menu-item">
        <div class="arrow">
            <a class="down">Open / Close</a>
        </div>

        Menu Item

        <div class="extramenu hidden">
            Extra menu items
        </div>
    </div>

    <div class="menu-item">
        <div class="arrow">
            <a class="up">Open / Close</a>
        </div>

        Menu Item 2

        <div class="extramenu">
            Extra menu items
        </div>
    </div>

    <div class="menu-item">
        <div class="arrow">
            <a class="down">Open / Close</a>
        </div>

        Menu Item 3

        <div class="extramenu hidden">
            Extra menu items
        </div>
    </div>
</div>

I select all "div.menu-item .arrow a" items, so I've 3 items. For each item I add a onclick event (that actually works fine).

What I need to archive is how to select the "closest" class .extramenu inside the div.menu-item. Then detect if the <a /> have a class .up or .down and if class == .up, add the class hidden; and if class == .down, remove the class hidden.

This a concept of what have to do, it's not javascript code:

var elements; // my list of elements

each(elements, function(element) {
    // here element is pointing to the ANCHOR
    add_event(element, "onclick", function(e) {
        var submenu; // here I need to detect the submenu closest to my anchor
        var state; // here I need to know if the anchor has class up or down

        if (state == "up")
        {
            add_class(submenu, "hidden"); // hide the submenu div
            remove_class(element, "up"); // remove the class up
            add_class(element, "down"); // and add the class down
        }
        else if (state == "down")
        {
            remove_class(submenu, "hidden"); // remove the class to show the menu
            remove_class(element, "down"); // remove the class down
            add_class(element, "up"); // and add the class up
        }
    });
});

Thank you guys and sorry if it's not well explained, I did my best!

---

element.querySelectorAll allows you to select elements by CSS selector.

element.classList allows you to access the classes of an element

add_event(element, "onclick", function(e) {
    var el = e.target, state;
    var parent = el.parentNode;
    while (!parent.classList.contains('menu-item')) {
        parent = parent.parentNode;
    }
    var submenu = parent.querySelector('extramenu');
        if (el.classList.contains('up')) {
        state = 'up';
    } else {
        state = 'down'
    }

    /* ... */
});

You can write the rest of the pseudo code yourself.

I'm assuming your already using Modernizr for supporting legacy browsers like IE8. If your not, then do so.

---

Maybe not exactly the way you want to do this but if class up or down would be added to parent of the a ie div.arrow you could do all of the hiding/showing with css combinator +. like this:

.arrow.down + .extramenu {
  /* the same styles as with hidden class */
}

---

This is the code you are looking for. Tested in FF5, should be cross-browser.

// use in your add_event function  
var submenu = element.parentNode.nextSibling;
while(submenu && (submenu.nodeName!="DIV" || submenu.className.indexOf("extramenu")==-1)) submenu = submenu.nextSibling;
var state = element.className;