Is there a good way to attach JavaScript objects to HTML elements?

I want to associate a JavaScript object with an HTML element. Is there a simple way to do this?

I noticed HTML DOM defines a setAttribute method and it looks like this is defined for arbitrary attribute name. However this can only set string values. (You can of course use this to store keys into a dictionary.)

Specifics (though I'm mostly interested in the general question):

Specifically, I have HTML elements representing nodes in a tree and I'm trying to enable drag-and-drop, but the jQuery drop event will only give me the elements being dragged and dropped.

The normal pattern for getting information to event handlers seems to be to create the HTML elements at the same time as you are creating JavaScript objects and then to define event handlers by closing over these JavaScript objects - however this doesn't work too well in this case (I could have a global object that gets populated when a drag begins... but this feels slightly nasty).

JavaScript objects can have arbitrary properties assigned to them, there's nothing special you have to do to allow it. This includes DOM elements; although this behaviour is not part of the DOM standard, it has been the case going back to the very first versions of JavaScript and is totally reliable.

var div= document.getElementById('nav');
div.potato= ['lemons', 3];

Have you looked at the jQuery data() method? You can assign complex objects to the element if you want or you can leverage that method to hold a reference to an object (or some other data) at the very least.