DataTransfer

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.

This object is available from the dataTransfer property of all drag events. It cannot be created separately (i.e. there is no constructor for this object).

Properties

Standard properties

DataTransfer.dropEffect

Gets the type of drag-and-drop operation currently selected or sets the operation to a new type. The value must be none, copy, link or move.

DataTransfer.effectAllowed

Provides all of the types of operations that are possible. Must be one of none, copy, copyLink, copyMove, link, linkMove, move, all or uninitialized.

DataTransfer.files

Contains a list of all the local files available on the data transfer. If the drag operation doesn't involve dragging files, this property is an empty list.

DataTransfer.items Read only

Gives a DataTransferItemList object which is a list of all of the drag data.

DataTransfer.types Read only

An array of strings giving the formats that were set in the dragstart event.

Gecko properties

DataTransfer.mozCursor

Gives the drag cursor's state. This is primarily used to control the cursor during tab drags.

DataTransfer.mozItemCount Read only

Gives the number of items in the drag operation.

DataTransfer.mozSourceNode Read only

The Node over which the mouse cursor was located when the button was pressed to initiate the drag operation. This value is null for external drags or if the caller can't access the node.

DataTransfer.mozUserCancelled Read only

This property applies only to the dragend event, and is true if the user canceled the drag operation by pressing escape. It will be false in all other cases, including if the drag failed for any other reason, for instance due to a drop over an invalid location.

Methods

Standard methods

DataTransfer.clearData()

Remove the data associated with a given type. The type argument is optional. If the type is empty or not specified, the data associated with all types is removed. If data for the specified type does not exist, or the data transfer contains no data, this method will have no effect.

DataTransfer.getData()

Retrieves the data for a given type, or an empty string if data for that type does not exist or the data transfer contains no data.

DataTransfer.setData()

Set the data for a given type. If data for the type does not exist, it is added at the end, such that the last item in the types list will be the new format. If data for the type already exists, the existing data is replaced in the same position.

DataTransfer.setDragImage()

Set the image to be used for dragging if a custom one is desired.

Gecko methods

DataTransfer.addElement()

Sets the drag source to the given element.

DataTransfer.mozClearDataAt()

Removes the data associated with the given format for an item at the specified index. The index is in the range from zero to the number of items minus one.

DataTransfer.mozGetDataAt()

Retrieves the data associated with the given format for an item at the specified index, or null if it does not exist. The index should be in the range from zero to the number of items minus one.

DataTransfer.mozSetDataAt()

A data transfer may store multiple items, each at a given zero-based index. mozSetDataAt() may only be called with an index argument less than mozItemCount in which case an existing item is modified, or equal to mozItemCount in which case a new item is added, and the mozItemCount is incremented by one.

DataTransfer.mozTypesAt()

Holds a list of the format types of the data that is stored for an item at the specified index. If the index is not in the range from 0 to the number of items minus one, an empty string list is returned.

Example

Every method and property listed in this document has its own reference page and each reference page either directly includes an example of the interface or has a link to an example.

Specifications

Browser compatibility

[1] Partial support refers to not supporting DataTransfer.setDragImage() [CanIUse.com].

[2] Does not support DataTransfer.items property.

[3] As of Firefox 52, the DataTransfer.types property returns a frozen array of DOMStrings as per spec, rather than a DOMStringList.

See also

• Drag and drop
• Drag Operations
• Recommended Drag Types
• Dragging and Dropping Multiple Items