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 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 dragenter
and 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 dragenter
and dragover
events, dropEffect
should be modified if a different action is desired than the action that the user is requesting.
For the drop
and dragend
events, dropEffect
will be set to the action that was desired, which will be the value dropEffect
had after the last dragenter
or dragover
event. In a dragend
event, for instance, if the desired dropEffect is "move", then the data being dragged should be removed from the source.
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.
This example shows the use of the dropEffect
and effectAllowed
properties.
<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>
div {
margin: 0em;
padding: 2em;
}
#source {
color: blue;
border: 1px solid black;
}
#target {
border: 1px solid black;
}
function dragstart_handler(ev) {
console.log(
`dragStart: dropEffect = ${ev.dataTransfer.dropEffect} ; effectAllowed = ${ev.dataTransfer.effectAllowed}`,
);
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();
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();
ev.dataTransfer.dropEffect = "move";
}