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HTML Drag and Drop

HTML Drag and Drop (DnD) is a feature of HTML5. It is a powerful user interface concept which is used to copy, reorder and delete items with the help of mouse. You can hold the mouse button down over an element and drag it to another location. If you want to drop the element there, just release the mouse button.

If you want to achieve the Drag and Drop functionality in traditional HTML4, you must either have to use complex JavaScript programming or other JavaScript frameworks like jQuery etc.

Events for Drag and Drop feature​

EventDescription
DragIt fires every time when the mouse is moved while the object is being dragged.
DragstartIt is a very initial stage. It fires when the user starts dragging object.
DragenterIt fires when the user moves his/her mouse cursor over the target element.
DragoverThis event is fired when the mouse moves over an element.
DragleaveThis event is fired when the mouse leaves an element.
DropDrop It fires at the end of the drag operation.
DragendIt fires when user releases the mouse button to complete the drag operation.

HTML5 Drag and Drop Example​

note

To understand this example, you must have the knowledge of JavaScript.


<script>
    function allowDrop(ev) {
        ev.preventDefault();
    }

    function drag(ev) {
        ev.dataTransfer.setData("text/html", ev.target.id);
    }

    function drop(ev) {
        ev.preventDefault();
        var data = ev.dataTransfer.getData("text/html");
        ev.target.appendChild(document.getElementById(data));
    }
</script>
<p>Drag the image into the rectangle:</p>
<div id="div1" style="width:350px;height:100px;padding:10px;border:1px solid #aaaaaa;"
     ondrop="drop(event)" ondragover="allowDrop(event)"></div>
<br>
<img id="drag1" src="/path/myimage.png" alt="Image"
     draggable="true" ondragstart="drag(event)"/>

In the above example, we have used ondrop and ondragover events on div element, and ondragstart event on img tag.

note

MouseEvent is not fired during drag operation.

Steps during Drag and Drop operations​

Make an Element Draggable​

First of all: To make an element draggable, set the draggable attribute to true:

<img draggable="true">

What to Drag - ondragstart and setData()​

Then, specify what should happen when the element is dragged.

In the example above, the ondragstart attribute calls a function, drag(event), that specifies what data to be dragged.

The dataTransfer.setData() method sets the data type and the value of the dragged data:

function drag(ev) {
    ev.dataTransfer.setData("text", ev.target.id);
}

In this case, the data type is "text" and the value is the id of the draggable element ("drag1").

Where to Drop - ondragover​

The ondragover event specifies where the dragged data can be dropped.

By default, data/elements cannot be dropped in other elements. To allow a drop, we must prevent the default handling of the element.

This is done by calling the event.preventDefault() method for the ondragover event:

event.preventDefault()

Do the Drop - ondrop​

When the dragged data is dropped, a drop event occurs.

In the example above, the ondrop attribute calls a function, drop(event):

function drop(ev) {
    ev.preventDefault();
    var data = ev.dataTransfer.getData("text");
    ev.target.appendChild(document.getElementById(data));
}

Code explained:

  • Call preventDefault() to prevent the browser default handling of the data (default is open as link on drop)
  • Get the dragged data with the dataTransfer.getData() method. This method will return any data that was set to the same type in the setData() method
  • The dragged data is the id of the dragged element ("drag1")
  • Append the dragged element into the drop element

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