Using custom options with KnockoutJS Drag and Drop

I was recently doing some work involving Knockout and needed to implement drag / drop (with jQuery UI draggable and droppable)

I stumbled across this post from Wilsonhut that shows how to use custom binding to attach drag and drop functionality to your view model.

Since that post (and previous posts in the series) covers that in detail, I won’t elaborate.
However, I had a requirement to be able to use some of my own options, for example appendTo.

To do this, I slightly modified the handler as follows:

 (function ($, ko) {
    var _dragged, _hasBeenDropped, _draggedIndex;
    ko.bindingHandlers.drag = {
        init: function (element, valueAccessor, allBindingsAccessor, viewModel) {
            var dragElement = $(element);

            var dragOptions = {
                helper: function () {
                    return dragElement.clone().addClass("ui-dragon");
                },
                revert: true,
                revertDuration: 0,
                start: function () {
                    _hasBeenDropped = false;
                    _dragged = ko.utils.unwrapObservable(valueAccessor().value);
                    if ($.isFunction(valueAccessor().value)) {
                        valueAccessor().value(undefined);
                        dragElement.draggable("option", "revertDuration", 500);
                    } else if (valueAccessor().array) {
                        _draggedIndex = valueAccessor().array.indexOf(_dragged);
                        valueAccessor().array.splice(_draggedIndex, 1);
                    }
                },
                stop: function (e, ui) {
                    if (!_hasBeenDropped) {
                        if ($.isFunction(valueAccessor().value)) {
                            valueAccessor().value(_dragged);
                        } else if (valueAccessor().array) {
                            valueAccessor().array.splice(_draggedIndex, 0, _dragged);
                        }
                    }
                },
                cursor: 'default'
            };

            var customDragOptions = ko.utils.unwrapObservable(valueAccessor().dragOptions);
            for (var attrname in customDragOptions) { dragOptions[attrname] = customDragOptions[attrname]; }

            dragElement.draggable(dragOptions).disableSelection();
        },
        update: function (element, valueAccessor, allBindingsAccessor, viewModel) {
            var dragElement = $(element);
            var disabled = !!ko.utils.unwrapObservable(valueAccessor().disabled);
            dragElement.draggable("option", "disabled", disabled);
        }
    };

    ko.bindingHandlers.drop = {
        init: function (element, valueAccessor, allBindingsAccessor, viewModel) {
            var dropElement = $(element);
            var dropOptions = {
                tolerance: 'pointer',
                drop: function (event, ui) {
                    _hasBeenDropped = true;
                    valueAccessor().value(_dragged);
                    ui.draggable.draggable("option", "revertDuration", 0);
                }
            };
            dropElement.droppable(dropOptions);
        },
        update: function (element, valueAccessor, allBindingsAccessor, viewModel) {
            var dropElement = $(element);
            var disabled = !!ko.utils.unwrapObservable(valueAccessor().disabled);
            dropElement.droppable("option", "accept", disabled ? ".nothing" : "*");
        }
    };
})(jQuery, ko);

This now allows me to do the following, with it still working as before: