Year ago I published a HTML5 Multi File Upload Control on openntf, now I extended it with drag & drop capability. And after doing some research, it was suprisingly easy.
First you need the custom control, download it here from openntf.
Then you need to add a div as target for dropping files:
Drop files here
Add some CSS to make the div pretty.
Finally you need to add this CSJS to the end of the custom control:
In the drop event we get the list of files dropped onto the div from the dataTransfer object, and we can put this list of file objects to the ynUploader_worker function which is already defined in the custom control.
I tested this in Chrome, Firefox and IE11 and – what a pleasant suprise – it works in all of them, even in IE.