Getting all visible elements using MooTools

Question

I am moving from jQuery to MooTools (for the fun..) and I have this line of code :

$subMenus = $headMenu.find('li ul.sub_menu:visible');

How I can write this in mootools?
I know that I can use getElements but How I can check for visible ul?(I am using this(:visible) selector a lot).

Edit -

I implemented my own function :

  function findVisibleElements(elementsCollection){
    var returnArray = [];
    elementsCollection.each(function(el){
      if(el.getStyle('display') === 'block'){
        returnArray.push(el);
      }
    });

    return returnArray;
  }

And what i want is to slide up all the visible sub menu, this is what I wrote :

// Sliding up the visible sub menus 
if( visibleSubMenus.length > 0 ){
  visibleSubMenus.each(function(el){
      var slider = new Fx.Slide(el, {duration: 2000});
      slider.slideOut();
  });
}

Why my code isn`t working?My function is working, and the problem is with the Fx.Slide.
I added mootools more with Fx.Slide.

Answer 1

Just extend the selector functionality - it's MooTools!

$extend(Selectors.Pseudo, {
    visible: function() {
        if (this.getStyle('visibility') != 'hidden' && this.isVisible() && this.isDisplayed()) {
            return this;
        }
    }
});

After that just do the usual $$('div:visible') which will return the elements that are visible.

Check out the example I've created: http://www.jsfiddle.net/oskar/zwFeV/