JavaScript and Facelets

Did you know that you're not allowed to use the full syntax of JavaScript language with Facelets? Well, I didn't and it took me over 4 hours to find that out. Let me explain:

Here's a simple JS function that will cause the rendering engine swallow it's own tongue and spit a nasty error message:

  <script>
function doSomething(items) {
  if(items.length > 0 && items.length < 5)
    return;
}
  </script>

First of all the < and > are not valid characters in XML so they are not valid in Facelets as well. And if you substitute them by &lt; it will be rendered as &lt; which makes the usage of < character impossible.
The same situation is with > sign as well as with && operator.

Of course you might say that my doSomething function makes no sense - it's for educational purposes only!

May the spirits protect us from Facelets!