jQuery UI Sortable, how to determine current location and new location in update event?

Question

I have:

<ul id="sortableList">
     <li>item 1</li>
     <li>item 2</li>
     <li>item 3</li>
</ul>

I have wired into the update: function(event, ui) { } but am not sure how to get the original and new position of the element. If i move item 3 to be above item 1, I want the original position to be 2 (0 based index) and the new position of item 3 to be 0.

Answer 1

$('#sortable').sortable({
    start: function(e, ui) {
        // creates a temporary attribute on the element with the old index
        $(this).attr('data-previndex', ui.item.index());
    },
    update: function(e, ui) {
        // gets the new and old index then removes the temporary attribute
        var newIndex = ui.item.index();
        var oldIndex = $(this).attr('data-previndex');
        $(this).removeAttr('data-previndex');
    }
});

Answer 2

When the update function is invoked the ui.item.sortable has not been updated, however the UI element has visually moved.
This allows you in the update function to get old position and new position.

   $('#sortable').sortable({    
        update: function(e, ui) {
            // ui.item.sortable is the model but it is not updated until after update
            var oldIndex = ui.item.sortable.index;

            // new Index because the ui.item is the node and the visual element has been reordered
            var newIndex = ui.item.index();
        }    
});

Answer 3

You have several possibilities to check the old and the new position. I would put them into arrays.

$('#sortable').sortable({
    start: function(e, ui) {
        // puts the old positions into array before sorting
        var old_position = $(this).sortable('toArray');
    },
    update: function(event, ui) {
        // grabs the new positions now that we've finished sorting
        var new_position = $(this).sortable('toArray');
    }
});

And you can then easily extract what you need.

Answer 4

I was looking for an answer to the same issue. based on what Frankie contributed, I was able to get both the start and end "orders". I had an issue with variable scope using the var, so I just stored them as .data() instead of local vars:

$(this).data("old_position",$(this).sortable("toArray"))

and

$(this).data("new_position",$(this).sortable("toArray"))

now you can call it up like this (from the update/end functions):

console.log($(this).data("old_position"))
console.log($(this).data("new_position"))

Credit still goes to Frankie :)