The source is here:
The code is pretty much idiomatic jQuery js following most of their style rules, layout rules and standard constructs so it's obviously been written as a jQuery extension. He must know jQuery well, hence why not use it?
As for why, well I spotted a bit of sizzle, jQuery.data and the event framework in one pass of a small code base. Given the nature of the library I can even guess what they're all for without reading the code.
Quite a lot more than the inevitable each that is also in there.
This seems to be the new 'cool'. "Why jQuery whine", whine, whine.
> You've got jQuery on your own site. Why are you moaning about it?
It was a theme requirement, also, Tu Quoque.
> He must know jQuery well, hence why not use it?
Because dependency for 200 lines of code.
> Quite a lot more than the inevitable each that is also in there.
Then the rest of your reply was redundant, wasn't it...
May be he does not. May be He uses Dojo, Prototype or any other JS library.
At least jQuery doesn't extends Object and Array like other libraries so it's quite safe to have as an extra dependency.
And there's your answer: The "cost" of depending on jQuery is small since so many things depend on it that most potential users probably already pull it in.
Ii your website uses the Google CDN to download jQuery new visitors will often not even download jQuery when arriving at your website because their browser probably has it already cached from visiting one of the dozens of other websites they have visited.
Some uses are unnecessary, eg. using `closest` to get the container form element. `element.form` can be used on any form input or control to access the form itself.
I dunno though. I don't like adding jQuery as a dependency but there are still some cases where it's just pragmatic, especially with handling events.