[ra3]

>"A correct answer to this will demonstrate both an understanding of basic computer science principles as well as a deeper knowledge of what jQuery is doing behind the scenes."

How does the referenced jquery statement represent basic CS principles? OOP? Definitely not that.

[whatevsmate]

The referenced jQuery statement gives the candidate a chance to speak on: selector complexity (id look ups vs traversing to find descendant elements), first-class functions (passing a function reference to the .on() method), regular expressions (to add class names to an existing class attribute in older browsers that don't have .classList property on elements). There are probably other things but those are just a few off the top of my head.