问题
I wish to create an outline around an element which has a margin for drag-and-drop purposes, so that the user can visually see that the cursor is in the centre of the space that will be taken up on drop. As far as I can see, the only way to achieve this is by creating a wrapper div with a border (or outline) for the duration of the drag, and focusing the drag on the wrapper. Is there a more efficient way?
来源：https://stackoverflow.com/questions/41502211/is-there-any-way-to-create-an-outline-around-an-elements-margins-besides-creati