jQuery data() returns undefined, attr() returns integer

OK. I found the problem by interpreting jQuery docs.

When you write:

$embellishment.data("embellishmentId");

it is handled by jQuery as compound attribute:

<div data-embellishment-id="3"></div>

So, to solve the problem you can use lower case in the data key otherwise it just addresses the different attribute.

<!-- HTML -->
<div data-embellishmentid="3"></div>

// JavaScript
$embellishment.data("embellishmentid");