What does this line of code in UI sortable mean?

I am using the UI jquery sortable plugin and have found some code that I am going to use but there is one part I don't understand. It is "onChange: "function(serialized) { widgets_positions(); }"

onChange doesn't appear in the documentation. Widgets_开发者_开发百科positions is a function that I understand about which tracks the positions of the objects being moved around. But I need to understand the 'onChange: function(serialized)' part.

                $('#col').Sortable(
                    {
                        accept: 'widget',
                        opacity: 0.5,
                        helperclass: 'helper',
                        onChange: function(serialized) { widgets_positions(); },
                        handle: '.widget_title_bar'
                    }
                );

I would imagine that is supposed to be change:

    $( ".selector" ).sortable({
   change: function(event, ui) { ... }
});

I have used the change event before when the order of the list is changed. ui gives you access to the dom element changed.

You could put your function call in the change event.