The DragEvent interface is a DOM event that represents a drag and drop interaction. The user initiates a drag by placing a pointer device (such as a mouse) on the touch surface and then dragging the pointer to a new location (such as another DOM element). Applications are free to interpret a drag and drop interaction in an application-specific way.
HTML Drag and Drop interfaces enable web applications to drag and drop files on a web page. This document describes how an application can accept one or more files that are dragged from the underlying platform's file manager and dropped on a web page.
The DataTransfer object is used to hold the data that is being dragged during a drag and drop operation. It may hold one or more data items, each of one or more data types. For more information about drag and drop, see HTML Drag and Drop API.
The DataTransferItem object represents one drag data item. During a drag operation, each drag event has a dataTransfer property which contains a list of drag data items. Each item in the list is a DataTransferItem object.
The read-only DataTransferItem.type property returns the type (format) of the DataTransferItem object representing the drag data item. The type is a Unicode string generally given by a MIME type, although a MIME type is not required.
The DataTransferItemList object is a list of DataTransferItem objects representing items being dragged. During a drag operation, each DragEvent has a dataTransfer property and that property is a DataTransferItemList.
The DataTransferItemList.add() method creates a new DataTransferItem using the specified data and adds it to the drag data list. The item may be a File or a string of a given type. If the item is successfully added to the list, the newly-created DataTransferItem object is returned.