HTML Drag and Drop API

Expert

(, )

By SamK

Category(s)

Web Design

Web Development

Topic(s)

HTML

In HTML, any element can be made draggable.

Drag and drop is a widely used feature that allows you to "grab" an object and move it to a different location.

HTML Drag and Drop Example

The following is a basic drag and drop example:

<!DOCTYPE HTML>
<html>
<head>
<script>
function dropFn(e) {
 e.preventDefault();
}
function drag(e) {
 e.dataTransfer.setData("text", e.target.id);
}
function drop(e) {
 e.preventDefault();
 var data = e.dataTransfer.getData("text");
 e.target.appendChild(document.getElementById(data));
}
</script>
</head>
<body>
<div id="ndiv" ondrop="drop(event)" ondragover="dropFn(event)"></div>
<img id="idrag" src="image.png" draggable="true" ondragstart="drag(event)" width="300" height="200">
</body>
</html>

Drag and Drop Demo

The above preview shows the <div> and <img> elements before drag and drop, and the below preview shows these elements after drag and drop.

DRag and Drop Demo

How it Works:

Make an Element Draggable

First, 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(e), that specifies what data to be dragged.

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

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

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

Where to Drop - ondragover

The ondragover event determines 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 behavior.

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

 e.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(e):

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

Code explained:

Call preventDefault() to stop the browser's default handling of the data (which is to open as a link on drop).
Use the dataTransfer.getData() method to retrieve the dragged data. This method returns any data set to the same type in the setData() method.
The dragged data is the ID of the dragged element ("idrag").
Append the dragged element to the drop target.

This was a simple HTML Drag and Drop tutorial. You'll learn more about this in our next tutorials.

Please check below options for the links to our previous or next tutorial.