Given it took Nathan a reasonably small amount of time to research and learn the correct answer, what disqualifies him from being (or quickly becoming) a skilled developer for your startup?
In other words, what's the minimum skill and knowledge level you'd accept, given that the applicant know how to learn the rest? Is that level arbitrary?
"Ok, draw me a square"
[proceeds to fail at squiggling something resembling a triangle]
For every job there is a hard, arbitrary skill floor.
Heck, we can't even decide what a web developer actually does, as opposed to a web designer, or "growth hacker", or UI/UX "expert", or back-end programmer.
How can we set a minimum when we can't clearly define the task beforehand?
This is not even testing an obscure application of closures. I mean, the trick here is not knowing about closures, but about knowing the details of the setTimeout function -- specifically, that there is a corresponding clearTimeout function (which, as a non-specifically frontend developer, I had long forgotten if I ever knew it).
That's not testing programming competency, that's testing knowledge of the JS standard library, and secondarily knowledge of closures. I mean, it's a legitimate thing to test for, but let's not pretend it's somehow analogous to fizz buzz.
Edit: And none of you even mentioned the error in his code, which another commenter pointed out: wrong function. It should have been clearTimeout
I've been asked similar questions in interviews, and when I haven't known the little bit of factual information required (in this case the existence of setTimeout and clearTimeout), I've asked to Google it, and my interviewers have always been more than happy to let me. I've passed interviews doing this. I've even had friends who do interviews tell me that 'googling an answer' is often the correct answer.
I personally think the choice of setTimeout/clearTimeout was a really good one because almost all JS devs will know it, but it's also really easy to find online if you know what you're looking for. This test is really about coming up with a good way to solve a problem.
setTimeout is something I had to learn about very early in my web development career. The essentials of jQuery too. Callbacks too, unless all you need is someone who does mainly html+css with a bit of jQuery. The interviewer asked exactly the kind of question that I'd consider a 'minimum'.
Of course, as others have pointed out, it also depends on what you're looking for. If you're okay with someone who can learn a lot on the job, and if you don't mind that this person has some basic things to pick up on, you'll probably be focusing more on how the interviewee approaches the problem, and how they interact with you as the interviewer.
The OP's takeaway seems to be that he should have known setTimeout well enough to walk through a solution. With that approach I think anyone will have a similar experience, only it would be some other random question. The lesson learned should be to actually make the attempt and try anything at your disposal. Ask questions. Ask for hints. Don't just say "um, I don't know."
For one, setTimeout is pretty run of the mill. If you haven't come across a situation where you need to wait a period of time before initiating some event, you simply haven't coded much. If someone else had just nailed the question in the interview before him than—hoop or not—they've proven a skill he hasn't.
Even if we ignore this, the "What Really Happened" area sounds like he only admitted he doesn't know, and worse, that he doesn't know how to proceed. Another comment above asks if one small set back is really a deal breaker, but in my opinion, not attempting to overcome a problem you haven't seen before shows more about a candidate's abilities than simple knowledge. Prove you can find a solution when all you have is a basic idea of the problem. Take a hint and run with it. (The interviewer gave the method name as a hint!) Google the answer.
This post hints that the position was closer to entry level, so I would suspect that curiosity and autonomous problem solving are fundamental requirements for the role. When you're green a lot is going to be brand new, so you have to be able to learn on the spot and run with it.
In fact, this is the primary reason I'm trying to move away from 'vanilla' front-end to more heavy js or backend stuff.
Completely agree. They'll toss the resume of someone who is an expert in graph theory, because they really need someone who knows machine learning, completely unaccepting of the fact that someone willing and able to become an expert in graph theory can probably do the same on machine learning.
This all plays into the current trend of businesses not being willing to train employees.