HTML5 Drag and Drop anywhere on the screen

javascript html drag-and-drop

Drag and drop doesn't move elements around, if you want the element to move when you drop it then you have to set the new position of the element in the drop event. I've done an example which works in Firefox and Chrome, here are the key points:

function drag_start(event) {    var style = window.getComputedStyle(event.target, null);    event.dataTransfer.setData("text/plain",    (parseInt(style.getPropertyValue("left"),10) - event.clientX) + ',' + (parseInt(style.getPropertyValue("top"),10) - event.clientY));}

The dragstart event works out the offset of the mouse pointer from the left and top of the element and passes it in the dataTransfer. I'm not worrying about passing the ID because there's only one draggable element on the page - no links or images - if you have any of that stuff on your page then you'll have to do a little more work here.

function drop(event) {    var offset = event.dataTransfer.getData("text/plain").split(',');    var dm = document.getElementById('dragme');    dm.style.left = (event.clientX + parseInt(offset[0],10)) + 'px';    dm.style.top = (event.clientY + parseInt(offset[1],10)) + 'px';    event.preventDefault();    return false;}

The drop event unpacks the offsets and uses them to position the element relative to the mouse pointer.

The dragover event just needs to preventDefault when anything is dragged over. Again, if there is anything else draggable on the page you might need to do something more complex here:

function drag_over(event) {    event.preventDefault();    return false;}

So bind it to the document.body along with the drop event to capture everything:

var dm = document.getElementById('dragme');dm.addEventListener('dragstart',drag_start,false);document.body.addEventListener('dragover',drag_over,false);document.body.addEventListener('drop',drop,false);

If you want this to work in IE you'll need to convert the aside to an a element, and, of course, all the event binding code will be different. The drag and drop API doesn't work in Opera, or on any mobile browsers as far as I'm aware. Also, I know you said you don't want to use jQuery, but cross browser event binding and manipulating element positions are the sort of things that jQuery makes much easier.

javascript html drag-and-drop

Thanks for your answer. It works great in Chrome and Firefox. I tweaked it to work in IE.Below is the code.

 <!DOCTYPE html>    <html lang="en">      <head>        <meta charset="utf-8">        <meta name="generator" content="CoffeeCup HTML Editor (www.coffeecup.com)">        <meta name="dcterms.created" content="Fri, 27 Jun 2014 21:02:23 GMT">        <meta name="description" content="">        <meta name="keywords" content="">        <title></title>                <!--[if IE]>        <script src="http://html5shim.googlecode.com/svn/trunk/html5.js"></script>        <![endif]-->    	<style>    	li    	{           position:  absolute;          left: 0;          top: 0; /* set these so Chrome doesn't return 'auto' from getComputedStyle */          width: 200px;           background: rgba(255,255,255,0.66);           border: 2px  solid rgba(0,0,0,0.5);           border-radius: 4px; padding: 8px;    	}    	</style>    	<script>            function drag_start(event) {                var style = window.getComputedStyle(event.target, null);                var str = (parseInt(style.getPropertyValue("left")) - event.clientX) + ',' + (parseInt(style.getPropertyValue("top")) - event.clientY) + ',' + event.target.id;                event.dataTransfer.setData("Text", str);            }            function drop(event) {                var offset = event.dataTransfer.getData("Text").split(',');                var dm = document.getElementById(offset[2]);                dm.style.left = (event.clientX + parseInt(offset[0], 10)) + 'px';                dm.style.top = (event.clientY + parseInt(offset[1], 10)) + 'px';                event.preventDefault();                return false;            }            function drag_over(event) {                event.preventDefault();                return false;            }    	</script>      </head>      <body ondragover="drag_over(event)" ondrop="drop(event)">       <ul>              <li id="txt1" draggable="true" ondragstart="drag_start(event)"> Drag this text </li><br>              <li id="txt2" draggable="true" ondragstart="drag_start(event)"> Drag me</li>      </ul>      	   <p>I never am really satisfied that I understand anything; because, understand it well as I may, my comprehension can only be an infinitesimal fraction of all I want to understand about the many connections and relations which occur to me, how the matter in question was first thought of or arrived at, etc., etc.</p>      	   <p>In almost every computation a great variety of arrangements for the succession of the processes is possible, and various considerations must influence the selections amongst them for the purposes of a calculating engine. One essential object is to choose that arrangement which shall tend to reduce to a minimum the time necessary for completing the calculation.</p>      	   <p>Many persons who are not conversant with mathematical studies imagine that because the business of [Babbage’s Analytical Engine] is to give its results in numerical notation, the nature of its processes must consequently be arithmetical and numerical, rather than algebraical and analytical. This is an error. The engine can arrange and combine its numerical quantities exactly as if they were letters or any other general symbols; and in fact it might bring out its results in algebraical notation, were provisions made accordingly.</p>      	   <p>The Analytical Engine has no pretensions whatever to originate anything. It can do whatever we know how to order it to perform. It can follow analysis, but it has no power of anticipating any analytical revelations or truths. Its province is to assist us in making available what we are already acquainted with.</p>          </body>   </html>

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