Two notes here...

`jQuery` is aliased as `$` in the opening line, `jQuery(function($) {`, which will mean `$ == jQuery` even when `jQuery.noconflict` is used. *Inside* plugins where this is the case, I'd like to always use `$` for consistency.

We also have the [underscore](http://underscorejs.org) library available. Although jQuery provides some similar functionality, we generally use underscore for code / flow / check utilities because it is more comprehensive, and jQuery for DOM / ajax / etc. In this case, `_.contains(list, value)` ([docs](http://underscorejs.org/#contains)) provides the equivalent to `jQuery.inArray`.

Not sure how to explain this best... basically, it's underscore for language enhancements, jQuery for client-side things. Since we use underscore in our back-end code, it keeps conventions for logic / flow control consistent across the front and back end.