Transitions Between Images?

Hi, I'm unexperienced with javascript and I'm currently taking a course that requires that we use it, regardless of whether we have written it or not.

I'm currently working on a short webcomic, but I want to transition between frames in a specific way. My professor showed me an example of it, but failed to give me the link.

What I'm looking for is: transitions between images in which the images literally move out from the middle of the frame in a horizontal, vertical, or diagonal direction, with a fixed background behind the images. Does anyone know what I'm talking about?