You have distributed the JavaScript library to the user; you are required to comply with the GPL's requirements on distribution then. Whether this requires you to distribute the rest of the website is where things get complicated - I'd advise you to talk with a competent lawyer about your exact situation if you're even thinking about going that route, and keep in mind that this is at least violating the spirit of the licence, whether or not it violates the letter of the license as well.
