I ended up realizing that I could just use a client side "(confirm())" script and then do my SSJS logic after that.

 

This article helped: http://www.jmackey.net/groupwareinc/johnblog/johnblog.nsf/d6plinks/GROC-7GLFZG

Thanks for the response Jeremy.

I believe you may be able to use the onComplete event of the SSJS to notify a user as well.

 

Typically, you would set the value of a hidden input field to the value of the alert content with the SSJS, and then simply grab that value (typically innerHTML) with the CSJS and use it in your alert statement.

 

You'll find the onComplete event in All Properties when you have the SSJS selected in the Source pane (well, that's how I find it anyway!). 

var id = "myErrorMessages";

facesContext.addMessage(id,  new javax.faces.application.FacesMessage("Show this message to the user"));

 

If you do not want to use the default "Display Errors" control, you can also use (for instance) a Computed Field that reads the messages from the facesContext, e.g.:

var msgIt = facesContext.getMessages("myErrorMessages");

var msg = [];
while (msgIt.hasNext() ) {
        msg.push(msgIt.next().getSummary());
}
return msg.join("<br>");