the method is called when an item is moved into a possible drop landing during dnd
|source||HTMLElement||a DOM element on which a dnd action started|
|target||HTMLElement||a DOM element of a possible drop landing|
|ev||Event||a native HTML event|
|HTMLElement||a DOM element which will be saved as a drop target (to ignore a drop landing, return a null value)|
The method isn't purposed for direct call! It is an extension point.
You can override it with your own logic, but check drag-n-drop related events first, as they provide a much more convenient way for drag-n-drop handling.