Our advice would be to avoid using Javascript in your emails.
Here's why:
The vast majority of email clients block JavaScript from running or, more commonly, ignore it completely. This is due to security concerns, as Javascript can be used for malicious purposes. The few clients that do support limited Javascripts are generally regarded as insecure, so are not widely used.
If your layout depends upon a script, but the email client fails to execute it, your email will look malformed to the viewer and possibly cause them to mark it as spam.
You will want to stick to standard HTML/CSS to create your emails for maximum compatibility.