I'm not looking to burst your bubble or anything, but if this is for a job interview, I believe they expect a whole lot more from you. They gave you a deceivingly simple task and maybe I'm wrong here, but I think that they expect much more from you than a simple function and I think that they expect much more from you than a simple jQuery widget.
While any of the simpler approach would be enough to complete the task, I believe they expect you to be familiar with more advanced topics and techniques. Personally, I think that that's why they mentioned jQuery together with IE9+. jQuery starting with v2 has dropped support for IE8- and is also supporting a modular approach.
They will asses your level depending on your approach. You seem to have trouble coping with terms like component, instances, domain. When you mix together OO, AMD and modular jQuery, for a JS newbie things start to get real crazy real fast. There's a lot of ground to cover. Let me know how it goes, and, after New Year, if you still want, we could get into this.