javascript prototype problem

Question

So I have a rather basic javascript problem which I have been slamming my head into a wall over for awhile:

<div class='alist'>
   <ul> 
       <li class='group_1'> An Item </li>
       <li class='group_1'> An Item </li>
       <li class='group_2'> An Item </li>
   </ul>
</div>

<div class='alist'>
   <ul> 
       <li class='group_1'> An Item </li>
       <li class='group_1'> An Item </li>
       <li class='group_2'> An Item </li>
   </ul>
</div>


<script>
function toggle_item( num ){
    $$( 'li.group_' + num ).invoke('toggle');
}
</script>

Basically, I need to create a sweeper that sets the div to display:none if all the li are display:none.

I think it would start like:

function sweep(){
    $$('div.alist').each( function( s ) {
      ar = s.down().children
    }); 
} 

Any suggestions for good tutorials would be welcome as well

Answer 1

You could use the select() method of Element to find all li descendants. And run a method Array.all for each li and check if all return true. Hide the div if all return true.

function sweep() {
    // check each div
    $$('div.alist').each(function(element) {
        var listItems = element.select('li');
        // are the list items of this div hidden?
        var listItemsHidden = listItems.all(function(item) {
            return item.visible();
        });
        // hide the div too if so
        if(listIemsHidden) {
            element.hide();
        }
    });
}

This code is untested.

Answer 2

Something like this might get you started. You'll need to iterate through the children and check if they're visible. If any of them aren't, set a flag and break from the loop. If the flag is false then you don't need to hide the div.

function sweep(){
    $$('div.alist').each( function( s ) {
        var shouldHide = true;
        var children = s.down().childElements();
        children.each(function(li) {
            if(li.visible()) {
                shouldHide = false;
                throw $break;
            }
        });

        if(shouldHide) {
            s.hide();
        }
    }); 
} 

Answer 3

This is jQuery solution (Prototype must be something similar):

$('div.alist').css('display', function () {
        return $(this).find('li:visible').length < 1 ? 'none' : '';
    });