JQuery sortable lists and fixed/locked items

Here’s a hopefully bug-free version, updating as you drag. It’s generating the current desired positions of the items when sorting starts, which means you should be able to change the classes whenever you need, refresh the widget’s list items and you’re good to go.

It also uses the sortable’s built-in items property to prevent dragging the fixed items and to sort out any sorting problems at the top and the bottom of the list.

I tried to move the fixed items around, but that resulted in horribly buggy behaviour, especially when there are multiple fixed items in groups. The final solution detaches all fixed items from the list, adds a helper element to the front, then re-inserts the fixed elements to their desired position, which seems to fix all bugs.

Try the demo here: http://jsfiddle.net/PQrqS/1/

HTML:

<ul id="sortable">
    <li>oranges</li>
    <li class="static">apples</li>
    <li>bananas</li>
    <li>pineapples</li>
    <li>grapes</li>
    <li class="static">pears</li>
    <li>mango</li>
</ul>

CSS:

.static { color:red; }

li { background-color:whitesmoke; border:1px solid silver; width:100px; padding:2px; margin:2px; }

Javascript:

$('#sortable').sortable({
    items: ':not(.static)',
    start: function(){
        $('.static', this).each(function(){
            var $this = $(this);
            $this.data('pos', $this.index());
        });
    },
    change: function(){
        $sortable = $(this);
        $statics = $('.static', this).detach();
        $helper = $('<li></li>').prependTo(this);
        $statics.each(function(){
            var $this = $(this);
            var target = $this.data('pos');

            $this.insertAfter($('li', $sortable).eq(target));
        });
        $helper.remove();
    }
});