When I interview front-end developers, I take a wireframe mockup, or sometimes just a screenshot (either from a real product, or just make one up), and ask "how

When I interview front-end developers, I take a wireframe mockup, or sometimes just a screenshot (either from a real product, or just make one up), and ask "how would you implement this". I want to see if they know the toolkit, can make good choices, can discuss tradeoff (e.g. should something be a custom widget or a stock system), can discuss performance (what if that table had 100k items? would it still work?). Then I ask if they have suggestions to change or improve the design, just to see if they think of themselves as more of an implementer or as sharing the responsibility with the interaction designer (both have their place). Finally, I do make sure they can do simple coding tasks, and give them some questions to test their comp-sci background, though that wouldn't disqualify someone, it can help. Oh yeah, I also ask them to talk about how to make an interface feel responsive even though most actions can trigger a network call that may take several seconds to respond.