I didn't. If by "do server side work with Javascript" you mean that the JavaScript is generated on the server, then you are correct. But everything that's served to a browser is generated by the server, so that's kind of a trivial statement. Of course you can use whatever means a
Java web app provides to generate that script code, including customizations based on a user's session. But in terms of execution, JSPs and JavaScript are completely separate from one another.