DataTransfer: dropEffect property
{{APIRef("HTML Drag and Drop API")}}
The DataTransfer.dropEffect property controls the
feedback (typically visual) the user is given during a drag and drop operation. It will
affect which cursor is displayed while dragging. For example, when the user hovers over
a target drop element, the browser’s cursor may indicate which type of operation will
occur.
When the {{domxref("DataTransfer")}} object is created, dropEffect is set
to a string value. On getting, it returns its current value. On setting, if the new
value is one of the values listed below, then the property’s current value will be set
to the new value and other values will be ignored.
For the {{domxref("HTMLElement/dragenter_event", "dragenter")}} and {{domxref("HTMLElement/dragover_event", "dragover")}} events,
dropEffect will be initialized based on what action the user is requesting.
How this is determined is platform specific, but typically the user can press modifier
keys such as the alt key to adjust the desired action. Within event handlers for
{{domxref("HTMLElement/dragenter_event", "dragenter")}} and {{domxref("HTMLElement/dragover_event", "dragover")}} events, dropEffect should
be modified if a different action is desired than the action that the user is
requesting.
For the {{domxref("HTMLElement/drop_event", "drop")}} and {{domxref("HTMLElement/dragend_event", "dragend")}} events, dropEffect will
be set to the action that was desired, which will be the value dropEffect
had after the last {{domxref("HTMLElement/dragenter_event", "dragenter")}} or {{domxref("HTMLElement/dragover_event", "dragover")}} event. In a
{{domxref("HTMLElement/dragend_event", "dragend")}} event, for instance, if the desired dropEffect is “move”, then the
data being dragged should be removed from the source.
Value
A string representing the drag operation effect. The possible values are:
copy- : A copy of the source item is made at the new location.
move- : An item is moved to a new location.
link- : A link is established to the source at the new location.
none- : The item may not be dropped.
Assigning any other value to dropEffect has no effect and the old value is
retained.
Example
This example shows the use of the dropEffect and
{{domxref("DataTransfer.effectAllowed","effectAllowed")}} properties.
HTML
<div>
<p id="source" ondragstart="dragstart_handler(event);" draggable="true">
Select this element, drag it to the Drop Zone and then release the selection
to move the element.
</p>
</div>
<div
id="target"
ondrop="drop_handler(event);"
ondragover="dragover_handler(event);">
Drop Zone
</div>
CSS
div {
margin: 0em;
padding: 2em;
}
#source {
color: blue;
border: 1px solid black;
}
#target {
border: 1px solid black;
}
JavaScript
function dragstart_handler(ev) {
console.log(
`dragStart: dropEffect = ${ev.dataTransfer.dropEffect} ; effectAllowed = ${ev.dataTransfer.effectAllowed}`,
);
// Add this element's id to the drag payload so the drop handler will
// know which element to add to its tree
ev.dataTransfer.setData("text", ev.target.id);
ev.dataTransfer.effectAllowed = "move";
}
function drop_handler(ev) {
console.log(
`drop: dropEffect = ${ev.dataTransfer.dropEffect} ; effectAllowed = ${ev.dataTransfer.effectAllowed}`,
);
ev.preventDefault();
// Get the id of the target and add the moved element to the target's DOM
const data = ev.dataTransfer.getData("text");
ev.target.appendChild(document.getElementById(data));
}
function dragover_handler(ev) {
console.log(
`dragOver: dropEffect = ${ev.dataTransfer.dropEffect} ; effectAllowed = ${ev.dataTransfer.effectAllowed}`,
);
ev.preventDefault();
// Set the dropEffect to move
ev.dataTransfer.dropEffect = "move";
}
{{EmbedLiveSample('Example', 300, 250)}}
Specifications
{{Specifications}}
Browser compatibility
{{Compat}}