Draggable DOM Helper Deleted - Causes JS Errors on Next Drag

The helper isn't meant to work that way. The helper is always removed after the drag and therefore you're not returning a valid helper on the second drag.

Yep, that's my diagnosis - but should this be a feature request for the future? Allow a selector to be passed in the helper argument?

The jQuery UI team had an API design meeting a few months ago where we reviewed the API of all existing plugins. Here are the relevant notes about draggable's helper option:

keep helper (though try to find a better name), but change values

change "original" to false, meaning don't use a helper

change "clone" to true, meaning use a helper (that its cloning the original element is just an implementation detail, can be mentioned in the docs)

keep the function argument for customizing the helper

I don't think the use case for using existing DOM elements is that big. Cloning an existing element should work fine (and is easily implemented using a function). I'm not sure why you said "recreating the DOM every time is a pain." What is painful about it?

My specific scenario involves showing whether a CMS component is being inserted or moved, the icon of the component and the name of the component. Considering it's also for an enterprise web app, my helper's rounded corners require extra HTML and CSS to work in older versions of IE. Below is a rough replication of the HTML, which is why I think it lends itself more to a clone() or tmpl() rather than a "from scratch" creation.

<div id="mouseFollow">
   <div>
      <span></span>
      <span><img /></span>
      <span></span>
   </div>
</div>

I'm glad you could share the team discussion notes with me as it gives me a clearer picture. Thanks for the help Scott :)

Sure, you could easily do:

$( elem ).draggable({
    helper: function() {
        return $( "#mouseFollow" ).clone().removeAttr( "id" );
    }
});

or use .tmpl() instead of .clone() as you've said.

You could probably even build an extension that accepts a selector, but my main concern would be people not realizing that internally the extension would do a clone on the element found by the selector and they might end up with duplicate ids.

Also, the notes from the design meeting are gradually being posted on the blog and forum for feedback. It'll still be a few weeks before we get to draggable.