How do I disable a jquery-ui draggable?

It took me a little while to figure out how to disable draggable on drop—use ui.draggable to reference the object being dragged from inside the drop function:

$("#drop-target").droppable({
    drop: function(event, ui) {
        ui.draggable.draggable("disable", 1); // *not* ui.draggable("disable", 1);
        …
    }
});

HTH someone

I have a simpler and elegant solution that doesn't mess up with classes, styles, opacities and stuff.

For the draggable element - you add 'start' event which will execute every time you try to move the element somewhere. You will have a condition which move is not legal. For the moves that are illegal - prevent them with 'e.preventDefault();' like in the code below.

    $(".disc").draggable({
        revert: "invalid", 
        cursor: "move",
        start: function(e, ui){                
            console.log("element is moving");

            if(SOME_CONDITION_FOR_ILLEGAL_MOVE){
                console.log("illegal move");
                //This will prevent moving the element from it's position
                e.preventDefault();
            }    

        }
    });

You are welcome :)