Drag and Drop
Drag and drop is a very common feature. It is when you "grab" an object and drag it to a different location.In HTML5, drag and drop is part of the standard, and any element can be draggable.
Browser Support
Internet Explorer 9, Firefox, Opera 12, Chrome, and Safari 5 support drag and drop.Note: Drag and drop does not work in Safari 5.1.2.
HTML5 Drag and Drop Example
The example below is a simple drag and drop example:| <!DOCTYPE HTML> <html> <head> <script type="text/javascript"> function allowDrop(ev) { ev.preventDefault(); } function drag(ev) { ev.dataTransfer.setData("Text",ev.target.id); } function drop(ev) { ev.preventDefault(); var data=ev.dataTransfer.getData("Text"); ev.target.appendChild(document.getElementById(data)); } </script> </head> <body> <div id="div1" ondrop="drop(event)" ondragover="allowDrop(event)"></div> <img id="drag1" src="img_logo.gif" draggable="true" ondragstart="drag(event)" width="336" height="69" /> </body> </html> |
It might seem complicated, but lets go through all the different parts of a drag and drop event.
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); } |
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)); } |
- 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("Text") 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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