Jason Lee wrote in with this tip:

In a general session with James Gosling at JavaOne last week, Tor "NetBeans Guy" Norbye demoed the really nice JavaScript support that was just added to NetBeans (code completion, browser-compatibility warnings, syntax highlighting, refactoring, etc). He did so using YUI, and NetBeans did a very nice job with the code complete, etc. Really slick demo...

Sun has video of the session; I recommend downloading the mp4 file and queuing to 8:30 for the NetBeans section, where Norbye shows how easy it is to instantiate a YUI Rich Text Editor using the new NetBeans JavaScript support.