They might look at your open source application but only about 30 seconds at the readme only, so include screenshots and maybe they might look at that. They are probably just looking at the number of stars, forks, and any other number not related to the software.
In the case of web development or JavaScript almost every time they will throw a shotgun blast of newb syntax questions at you. Sometimes the questions are general and other times the interviewer is fishing for something of comfort to a personal code style. If they ask for any opinion or open-ended question respond with something critical or unpopular to see how the interviewer reacts. Failure to do so will endanger your ability to do anything creative or challenging.
As a bored and thoroughly under impressed candidate I really wished companies, who claim to be looking for senior developers, asked for the impossible to see what kind of answers they get. By impossible I really mean standard interview questions everywhere else. Examples:
* How do you achieve complete page load in less than a second?
* How do you achieve accessibility AA criteria without ARIA?
* How do you create custom components without a framework?
* Describe a means of broadcasting information to users in real time without polling a server.
* How do you persist/restore state without compromising page load time?
* How would you achieve real time status updates to/from users without negatively impacting usability or accessibility?