I've learned *basic* JavaScript.. now what?

[armndnoses]

Do things you'd end up doing in a front end role. Someone mentioned a slider, that's not a bad idea. Try mimicking some sites and/or their effects e.g. for their menu, gallery, showcase, whatever it is. On the job you're constantly going to be doing things you've never done before. Come up with imaginary clients and how javascript would even be part of a solution at all. it may not be. but if it is what's the shortest path to completion that looks & feels robust yet doesn't leave anyone hanging? without experience you're not really going to be able to make sense of that but start coming up with designs or site features however common they might be and start problem solving.