<!DOCTYPE html>
<title>drag &amp; drop - writing to dropEffect</title>
<style>
  body > div {
    height: 200px;
    width: 200px;
    background-color: orange;
    position: absolute;
    top: 8px;
    left: 8px;
  }
  body > div * {
    display: none;
  }
  body > div + div {
    background-color: navy;
    left: 250px;
  }
  body > div + div + div {
    background-color: fuchsia;
    left: 500px;
  }
  p:first-of-type {
    margin-top: 220px;
  }
</style>

<script>

window.onload = function() {
	var orange = document.getElementsByTagName('div')[0], fails = [], doneonce = false, seenevent = {};
  orange.ondragstart = function(e) {
    e.dataTransfer.setData('Text', 'dummy text');
		e.dataTransfer.effectAllowed = 'all';
		if( seenevent[e.type] ) { return; }
  	seenevent[e.type] = true;
    if( e.dataTransfer.dropEffect != 'none' ) {
			fails[fails.length] = e.type + ' dropEffect ' + e.dataTransfer.dropEffect + ' instead of none';
    }
    try{ e.dataTransfer.dropEffect = 'move' } catch(err) {
			fails[fails.length] = e.type + ' dropEffect threw on setting';
    }
    if( e.dataTransfer.dropEffect != 'move' ) {
			fails[fails.length] = e.type + ' dropEffect ' + e.dataTransfer.dropEffect + ' instead of move (seems to be readonly)';
    }
  };
  orange.ondrag = orange.nextSibling.ondragleave = function(e) {
		if( seenevent[e.type] ) { return; }
  	seenevent[e.type] = true;
    if( e.dataTransfer.dropEffect != 'none' ) {
			fails[fails.length] = e.type + ' dropEffect ' + e.dataTransfer.dropEffect + ' instead of none';
    }
    try{ e.dataTransfer.dropEffect = 'move' } catch(err) {
			fails[fails.length] = e.type + ' dropEffect threw on setting';
    }
    if( e.dataTransfer.dropEffect != 'move' ) {
			fails[fails.length] = e.type + ' dropEffect ' + e.dataTransfer.dropEffect + ' instead of move (seems to be readonly)';
    }
  };
  orange.nextSibling.ondragenter = function(e) {
  	e.preventDefault();
		if( seenevent[e.type] ) { return; }
  	seenevent[e.type] = true;
    if( e.dataTransfer.dropEffect != 'copy' ) {
			fails[fails.length] = e.type + ' dropEffect ' + e.dataTransfer.dropEffect + ' instead of copy';
    }
    try{ e.dataTransfer.dropEffect = 'move' } catch(err) {
			fails[fails.length] = e.type + ' dropEffect threw on setting';
    }
    if( e.dataTransfer.dropEffect != 'move' ) {
			fails[fails.length] = e.type + ' dropEffect ' + e.dataTransfer.dropEffect + ' instead of move (seems to be readonly)';
    }
  };
  orange.nextSibling.ondragover = function(e) {
  	e.preventDefault();
		if( seenevent[e.type] ) {
			e.dataTransfer.dropEffect = 'link';
			return;
		}
  	if( !doneonce ) {
	    if( e.dataTransfer.dropEffect != 'copy' ) {
				fails[fails.length] = e.type + ' dropEffect ' + e.dataTransfer.dropEffect + ' instead of copy';
	    }
	    try{ e.dataTransfer.dropEffect = 'move' } catch(err) {
				fails[fails.length] = e.type + ' dropEffect threw on setting';
	    }
	    if( e.dataTransfer.dropEffect != 'move' ) {
				fails[fails.length] = e.type + ' dropEffect ' + e.dataTransfer.dropEffect + ' instead of move (seems to be readonly)';
	    }
	  	doneonce = true;
	  } else {
	  	seenevent[e.type] = true;
	    if( e.dataTransfer.dropEffect != 'copy' ) {
				fails[fails.length] = e.type + ' dropEffect ' + e.dataTransfer.dropEffect + ' instead of copy on second attempt';
	    }
	    try{ e.dataTransfer.dropEffect = 'link' } catch(err2) {
				fails[fails.length] = e.type + ' dropEffect threw on setting';
	    }
	    if( e.dataTransfer.dropEffect != 'link' ) {
				fails[fails.length] = e.type + ' dropEffect ' + e.dataTransfer.dropEffect + ' instead of link on second attempt (seems to be readonly)';
	    }
	  	doneonce = true;
	  }
  };
  orange.nextSibling.ondrop = function(e) {
  	e.preventDefault();
		if( seenevent[e.type] ) { return; }
  	seenevent[e.type] = true;
    if( e.dataTransfer.dropEffect != 'link' ) {
			fails[fails.length] = e.type + ' dropEffect ' + e.dataTransfer.dropEffect + ' instead of link';
    }
    try{ e.dataTransfer.dropEffect = 'move' } catch(err) {
			fails[fails.length] = e.type + ' dropEffect threw on setting';
    }
    if( e.dataTransfer.dropEffect != 'move' ) {
			fails[fails.length] = e.type + ' dropEffect ' + e.dataTransfer.dropEffect + ' instead of move (seems to be readonly)';
    }
  };
  orange.ondragend = function(e) {
		if( seenevent[e.type] ) { return; }
  	seenevent[e.type] = true;
    if( e.dataTransfer.dropEffect != 'move' ) {
    	//under-specified in the spec, but part of the spec related to cancelling a drag says:
    	//"set the current drag operation to the value of the dropEffect attribute of the DragEvent
    	//object's dataTransfer object as it stood after the event dispatch finished."
    	//this does not cover successful drags, but it makes sense to be consistent
			fails[fails.length] = e.type + ' dropEffect ' + e.dataTransfer.dropEffect + ' instead of move';
    }
    try{ e.dataTransfer.dropEffect = 'copy' } catch(err) {
			fails[fails.length] = e.type + ' dropEffect threw on setting';
    }
    if( e.dataTransfer.dropEffect != 'copy' ) {
			fails[fails.length] = e.type + ' dropEffect ' + e.dataTransfer.dropEffect + ' instead of copy (seems to be readonly)';
    }
    if( !seenevent.dragstart ) {
			fails[fails.length] = 'dragstart did not fire';
    }
    if( !seenevent.drag ) {
			fails[fails.length] = 'drag did not fire';
    }
    if( !seenevent.dragenter ) {
			fails[fails.length] = 'dragenter did not fire';
    }
    if( !seenevent.dragover ) {
			fails[fails.length] = 'dragover did not fire enough times';
    }
    if( !seenevent.dragleave ) {
			fails[fails.length] = 'dragleave did not fire';
    }
    if( !seenevent.drop ) {
			fails[fails.length] = 'drop did not fire';
    }
   	document.getElementsByTagName('p')[0].innerHTML = fails.length ? ( 'FAIL: ' + fails.join('<br>') ) : 'PASS';
  };
};

</script>

<div draggable='true'></div><div></div><div></div>

<p>Use your pointing device to drag the orange box to the pink box, then back to the blue box, and release it.</p>
<noscript><p>Enable JavaScript and reload</p></noscript>