[metamemetics]

JavaScript for AJAX and loading new information would be developer yes, because that is all about querying and interfacing with the back-end.

Simple visual JavaScript effects for enhancing presentation and interface would be web-designer.

To me the key part of the term "web-designer" is web... you are creating design using the assembly languages of web browsers: HTML, CSS, JavaScript, and small quick-to-load chunks of graphics. Drawing is just the first planning step and there is nothing that makes it "web" specific other than an intention. Whereas in "graphic" design this is the end result. A graphic designer designs instructions for a graphics display process to display graphics, a web designer designs instructions for a web browser to display web pages.