Jon Udell has written an interesting introduction to E4X (ECMAScript for XML) on his weblog. I hadn't heard of E4X before. It's a proposed standard for adding formal XML datatypes to ECMAScript, the standard behind JavaScript. E4X hasn't hit any browsers yet, but thanks to Rhino, a Java-based JavaScript interpreter from the Mozilla project, Jon is able to demonstrate some examples using command-line JavaScript.
I was impressed with this glimpse into the future of JavaScript. You can define an XML structure as easily as an array or object, and the methods for working with XML are much simpler than I've seen for any other language. I'm sure I'll be talking about this more in the future as it moves closer to the mainstream.
