What validation did you expect? Just the @ and the dot? Or a bit more? The top level domains? Or even the existence of the domain name?
At any way, good thing to know is that Javascript´s regex is borrowed from Perl which is (very) commonly used. So you could just google the "usual" regexp
patterns for that and use it.
Also see
http://www.regular-expressions.info/javascript.html
And
http://www.regular-expressions.info/email.html
The linked site is in general quite useful if you want to learn about regexps. Bookmark it.