code: function (checker) {
              if (isFunction(checker)) {
                  this.options.drop.checker = checker;
  
                  return this;
              }
              if (checker === null) {
                  delete this.options.getRect;
  
                  return this;
              }
  
              return this.options.drop.checker;
          }
docs: /*\
  Interactable.dropChecker
  [ method ]
  
  DEPRECATED. Use interactable.dropzone({ checker: function... }) instead.
  
  Gets or sets the function used to check if a dragged element is
  over this Interactable.
  
  - checker (function) #optional The function that will be called when checking for a drop
  = (Function | Interactable) The checker function or this Interactable
  
  The checker function takes the following arguments:
  
  - dragEvent (InteractEvent) The related dragmove or dragend event
  - event (TouchEvent | PointerEvent | MouseEvent) The user move/up/end Event related to the dragEvent
  - dropped (boolean) The value from the default drop checker
  - dropzone (Interactable) The dropzone interactable
  - dropElement (Element) The dropzone element
  - draggable (Interactable) The Interactable being dragged
  - draggableElement (Element) The actual element that's being dragged
  
  > Usage:
  | interact(target)
  | .dropChecker(function(dragEvent,         // related dragmove or dragend event
  |                       event,             // TouchEvent/PointerEvent/MouseEvent
  |                       dropped,           // bool result of the default checker
  |                       dropzone,          // dropzone Interactable
  |                       dropElement,       // dropzone elemnt
  |                       draggable,         // draggable Interactable
  |                       draggableElement) {// draggable element
  |
  |   return dropped && event.target.hasAttribute('allow-drop');
  | }
  \