First of all, JavaScript is not Java. It has nothing to do with Java (The language and its associated technologies from Sun Microsystems). To be honest, I'm not even sure why it's called JavaScript.

The javascript file contains a method addToViewer (theUrl), I need to get the variable 'url' from the servlet into this method.

JavaScript (5.8 million users) As Java powered the back end, JavaScript (which, despite the name, really has nothing to do with Java) powers the front end of applications.